How does this character meaning become "small/tiny"? So many sources tell me that it's semantic 彳 + "phonetic" 𢼸, but what exactly is 𢼸? I've never seen this character elsewhere before. Could this possibly like 德 and 得, where the original character was missing the 彳 part? However, I haven't found any answer that explains the 𢼸 component, so was wondering if anyone can enlighten me, thanks.
「微」 (Baxter-Sagart OC: /*məj/), to travel [somewhere] under stealth. From semantic 「彳」 (to walk) and phonetic 「𣁋」 (/*məj/).
Strictly speaking, 「微」 is just a complexified character from 「𣁋」. Characters naturally become more complex over time for disambiguation purposes, as simpler characters tend to be used and reused for other senses or as rebus characters/phonetic loans, causing them to be overloaded with definitions and more easily subjected to shape distortions, and thus increasingly difficult to comprehend.
Since 「𣁋」 is the original character for the meaning small, slight, then in terms of glyph origins, 「微」 is built from semantic 「彳」 and doubly semantic and phonetic 「𣁋」 . 「彳」 is simply a semantic indicator appended on to 「微」 to extend the meaning small, slight to travelling under stealth.
So, all this begs the question - what exactly is 「𣁋」 supposed to be？
Glyph origins of 「𣁋」
「𣁋」 is constructed from semantic 「髟」 (picture of a person with long hair) and semantic 「攵・攴」 (picture of a hand holding a hitting implement > to strike, to hit), inferring the meaning delicate, slight through the action of cutting off a full growth of hair into a more elegant and delicate state.
(/*məj/) [means] delicate. From semantic 「人」 (person), semantic 「攴」 (to strike), and reduced phonetic 「豈」 (/*C.qʰˤəjʔ/).
is probably a misunderstanding. 「豈」 may have originated from an alteration of 「壴」 (picture of a drum) into 「豈」 (beating of victory drums > triumphant music, now written as 「凱」), and Shuōwén has confused the top part of 「豈」 with the top-[left] part of 「髟」.
For reference, shape derivation of 「豈」. Shapes 1-4 refer to 「壴」. Shape 5 is 「敳」, with the left-hand component as 「壴」 but the top-left part written as a rotated 「山」. This sets the scene for the confusion of 「豈」 and 「𣁋」 in Shuōwén. Forms 6-9 refer to 「豈」, which all inherit the (rotated) 「山」 shape.