-ly

(forms adjectives from nouns)

Wiktionary

Pronunciation: /li/ / [liː] / [lɪ]

suffix

Etymology: Etymology tree Proto-Indo-European *leyg-der. Proto-Germanic *līkąder. Proto-Germanic *-līkaz Proto-Germanic *-ê Proto-Germanic *-līkê Proto-West Germanic *-līkē Old English -līċe Middle English -ly English -ly From Middle English -ly, -li, -liche, from Old English -līċe.

Used to form adverbs from adjectives and nouns.
“sudden + -ly → suddenly”
“eerie + -ly → eerily”
Used to form company or brand names.
“book + -ly → Bookly”
“musical + -ly → Musical.ly”