interrogative particle, repetition of a tune small, tender
么 is a rare kanji with no clear standalone meaning. Its given glosses point to an interrogative particle, a repeated tune, and something small or tender, but these do not form one coherent conceptual center. Treat its meaning as uncertain.
The historical origin of 么 is uncertain. It may be a simplified or variant form, but its exact development is unclear.
The top stroke 丿 looks like a small hook, and the bottom 厶 resembles a curled shape. Picture a tiny, tender sprout curling out of the ground, asking a question with its delicate form.
For エウ, imagine a small, tender ewe (a young female sheep) bleating a repeated tune: ewe -> エウ, and the tiny lamb asks a question with its soft cry.