号
ゴウ, さけ.ぶ, よびな

nickname, number, item, title, pseudonym, name, call

JLPT3 G3 S5 F585

丂 is an object that extends before bending (compare 于). 号 is 口 mouth + 丂# both for the idea of bending and for the sound to simulate a cry or calling noise produced by bending the throat → *call*; *name* → *number*; *indicator*. In Japan, 号 is a Shinjitai (new character form) replacing 號.

[Full Kanji Etymology List]