staffs -> staves. I't explained on the wiki.

data/campaigns/The_Hammer_of_Thursagan/units/Dwarvish_Masked_Dragonguard.cfg

@@ -16,7 +16,7 @@
     cost=46
     usage=archer
 #textdomain wesnoth-units
-    description= _ "It is not clear why the Dragonguards are called what they are, a name given by their dwarven brethren. Some speculate that the name comes from their weapon of choice, these strange staffs that belch fire and death. Others have surmised that it is because such weapons would be a threat against even a true Dragon, should such a thing be seen again in the known world. Whatever the case, it is for these weapons that the guardians of the great Dwarven citadels are both renowned and feared; weapons that have broken the mightiest of warriors with a single blow."
+    description= _ "It is not clear why the Dragonguards are called what they are, a name given by their dwarven brethren. Some speculate that the name comes from their weapon of choice, these strange staves that belch fire and death. Others have surmised that it is because such weapons would be a threat against even a true Dragon, should such a thing be seen again in the known world. Whatever the case, it is for these weapons that the guardians of the great Dwarven citadels are both renowned and feared; weapons that have broken the mightiest of warriors with a single blow."
     image="units/masked_dragonguard.png"
     {DEFENSE_ANIM_RANGE "units/masked_dragonguard-defend.png" "units/masked_dragonguard-melee1.png" {SOUND_LIST:DWARF_HIT} melee}
     {DEFENSE_ANIM_RANGE "units/masked_dragonguard-defend.png" "units/masked_dragonguard.png" {SOUND_LIST:DWARF_HIT} ranged}

data/campaigns/The_Hammer_of_Thursagan/units/Dwarvish_Masked_Thunderguard.cfg

@@ -17,7 +17,7 @@
     cost=30
     usage=mixed fighter
 #textdomain wesnoth-units
-    description= _ "The Dwarven Thunderguards are famed for their curious weaponry, these strange staffs of wood and iron that make a thunderous noise in their anger. The machinations behind this weaponry are a mystery, a secret taken to the grave by the dwarves of Knalga who wield them, and are assumed to have even forged them. The most that is known are reports of dwarves pouring a strange black dust into the mouth of their weapons, which some say is a food to fuel the beast imprisoned within.
+    description= _ "The Dwarven Thunderguards are famed for their curious weaponry, these strange staves of wood and iron that make a thunderous noise in their anger. The machinations behind this weaponry are a mystery, a secret taken to the grave by the dwarves of Knalga who wield them, and are assumed to have even forged them. The most that is known are reports of dwarves pouring a strange black dust into the mouth of their weapons, which some say is a food to fuel the beast imprisoned within.
 
 Though a single shot from these ‘thundersticks’ can take several minutes to prepare, the results are seen by the Dwarves as being well worth the wait."
     die_sound={SOUND_LIST:DWARF_DIE}
@@ -183,4 +183,4 @@ Though a single shot from these ‘thundersticks’ can take several minutes to
             image="units/masked_thunderguard.png"
         [/frame]
     [/attack_anim]
-[/unit_type]
+[/unit_type]

data/core/units/dwarves/Dragonguard.cfg

@@ -18,7 +18,7 @@
     undead_variation=dwarf
     cost=46
     usage=archer
-    description= _ "It is not clear why the Dragonguards are called what they are, a name given by their dwarven brethren. Some speculate that the name comes from their weapon of choice, these strange staffs that belch fire and death. Others have surmised that it is because such weapons would be a threat against even a true Dragon, should such a thing be seen again in the known world. Whatever the case, it is for these weapons that the guardians of the great Dwarven citadels are both renowned and feared; weapons that have broken the mightiest of warriors with a single blow."
+    description= _ "It is not clear why the Dragonguards are called what they are, a name given by their dwarven brethren. Some speculate that the name comes from their weapon of choice, these strange staves that belch fire and death. Others have surmised that it is because such weapons would be a threat against even a true Dragon, should such a thing be seen again in the known world. Whatever the case, it is for these weapons that the guardians of the great Dwarven citadels are both renowned and feared; weapons that have broken the mightiest of warriors with a single blow."
     die_sound={SOUND_LIST:DWARF_DIE}
     {DEFENSE_ANIM_RANGE "units/dwarves/dragonguard-blade-defend-2.png" units/dwarves/dragonguard-blade-defend-1.png {SOUND_LIST:DWARF_HIT} melee}
     {DEFENSE_ANIM_RANGE "units/dwarves/dragonguard-defend.png" units/dwarves/dragonguard.png {SOUND_LIST:DWARF_HIT} ranged}

data/core/units/dwarves/Thunderguard.cfg

@@ -17,7 +17,7 @@
     undead_variation=dwarf
     cost=30
     usage=mixed fighter
-    description= _ "The Dwarven Thunderguards are famed for their curious weaponry, these strange staffs of wood and iron that make a thunderous noise in their anger. The machinations behind this weaponry are a mystery, a secret taken to the grave by the dwarves of Knalga who wield them, and are assumed to have even forged them. The most that is known are reports of dwarves pouring a strange black dust into the mouth of their weapons, which some say is a food to fuel the beast imprisoned within.
+    description= _ "The Dwarven Thunderguards are famed for their curious weaponry, these strange staves of wood and iron that make a thunderous noise in their anger. The machinations behind this weaponry are a mystery, a secret taken to the grave by the dwarves of Knalga who wield them, and are assumed to have even forged them. The most that is known are reports of dwarves pouring a strange black dust into the mouth of their weapons, which some say is a food to fuel the beast imprisoned within.
 
 Though a single shot from these ‘thundersticks’ can take several minutes to prepare, the results are seen by the Dwarves as being well worth the wait."
     die_sound={SOUND_LIST:DWARF_DIE}