organic substance obtained from muscular tissue, by 1843, from French creatine, from Greek kreas "flesh, meat" (from PIE root *kreue- "raw flesh") + chemical suffix -ine (2). Discovered 1832 by French physicist Michel-Eugène Chevreul (1786-1889) and named by him.
word-forming element in chemistry, often interchangeable with -in (2), though modern use distinguishes them; early 19c., from French -ine, the suffix commonly used to form words for derived substances, hence its extended use in chemistry. It was applied unsystematically at first (as in aniline), but now has more restricted use.
The French suffix is from Latin -ina, fem. form of -inus, suffix used to form adjectives from nouns, and thus is identical with -ine (1).
<a href="https://www.etymonline.com/word/creatinine">Etymology of creatinine by etymonline</a>
Harper, D. (n.d.). Etymology of creatinine. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/creatinine