creatine n.

*kreuə-, Proto-Indo-European root meaning "raw flesh."

It forms all or part of: 

creatine; creosote; crude; cruel; ecru; pancreas; raw; recrudesce; recrudescence.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kravis- "raw flesh," krura- "raw, bloody;" Greek kreas "flesh;" Latin crudus "bloody, raw; cruel," cruor "thick blood;" Old Irish cru "gore, blood," Middle Irish cruaid "hardy, harsh, stern;" Old Church Slavonic kry "blood;" Old Prussian krawian, Lithuanian kraūjas "blood;" Old English hreaw "raw," hrot "thick fluid, serum."

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).

"alkaline substance obtained by the action of acids on creatine," by 1847, from creatine + chemical suffix -ine (2).