触腕

Seemingly a Japanese coinage from Middle Chinese-derived 触 (shoku, “feeling; feeler”) +‎ 腕 (wan, “arm”). Appears during the mid- to late-1800s, in either the Edo period or Meiji period.

• IPA^(key): [ɕo̞kɯ̟β̞ã̠ɴ]

触(しょく)腕(わん) • (shokuwan) 

1. (zootomy) a tentacle: specifically, either of the two tentacles of a squid or cuttlefish that are longer than the other eight (technically called “arms”)
   • 1977, 竹村 よしお and 佐藤 魚水, 海の釣り魚, →ISBN

     普段(ふだん)は短(みじか)い ８本(はっぽん)の腕(うで)と同(おな)じく目立(めだ)たないようにしているが、接近(せっきん)するなり、ショットして触腕(しょくわん)を伸長(しんちょう)させて捕捉(ほそく)する。

     Fudan wa mijikai happon no ude to onajiku medatanai yō ni shite iru ga, sekkin suru nari, shotto shite shokuwan o shinchō sasete hosoku suru.

     Usually, like the eight shorter arms, [the two longer tentacles] also try not to stand out. However, as soon as [the cuttlefish] approaches [its prey], it shoots and extends its tentacles to capture it.

• 触(しょく)手(しゅ) (shokushu): an arm: specifically, one of the eight arms of an octopus or similar animal