乚 yǐn
“hidden, mysterious, secret; to conceal; small; minute”
On its own, an ordinary character; Cantonese jyut3. Readings and gloss from the Unicode Unihan database.
Carries Gadolinium
Transliterates syllable 1 of ga·do·li·nium: gadolinium → gá.
The reading drifted: the component is read yǐn, the element gá.