拳固 is read as げんこ (genko) and means fist.
げんこ
genko
けんじゅう
pistol
げんこつ
(clenched) fist
こぶし
fist
けんぽう
kenpō (martial arts)
けんとうせんしゅ
boxer
けんとうか
がんこ
stubborn
けんご
solid
ぎょうこ
coagulation
ようじんけんご
very cautious (watchful, vigilant)
どうしんけんご
being of firm (unshakable) faith and strict practice
ごうじょうがんこ
headstrong