Shinobi is the conjugation stem for 忍ぶ, which is a verb for “to conceal/hide”. Often times verb stems are used to create compound words - eg. Taberu means “to eat”, mono means “thing”. Tabe- is the conjugation steam for Taberu and you combine it with mono to make Tabemono, a.k.a. “eat thing” or “food”. So shinobi is…