忍
ニン, しの.ぶ, しの.ばせる, おし

endure, bear, put up with, conceal, secrete, spy, sneak

JLPT1 G7 S7 F1700

As per 刃# (flexible) + 心 heart/emotions → *bear*; *endure* (← heart that flexibly bears/endures burdens). *Stealth* and *concealment* are borrowed meanings → *secret*; *hide*; *incognito*; *sneak into/about*.

[Full Kanji Etymology List]