bilirubin (n.)

"yellow bitter liquid secreted by the liver that aids in digestion," 1660s, from French bile (17c.) "bile," also, informally, "anger," from Latin bilis "fluid secreted by the liver," also in old medicine one of the four humors (also known as choler), thus "bitterness of feeling, peevishness," supposedly caused by excess of bile (especially as black bile, 1797).

The Latin word is of uncertain origin. De Vaan notes apparent cognates for it in British Celtic (Welsh bustl, Middle Cornish bystel, Breton bestl "gall, bile") and writes, "since this word is only found in Italic and Celtic, it is possible that the word is not PIE." But, he adds, if it was borrowed from Celtic into Italic it might be from PIE root *bheid- "to split," which in Germanic has come to meaning "bite," and he notes that "'bile' is a biting substance."

Proto-Indo-European root meaning "red, ruddy." The only color for which a definite common PIE root word has been found. The initial -e- in the Greek word is because Greek tends to avoid beginning words with -r-.

It forms all or part of: bilirubin; corroborate; Eritrea; erysipelas; erythema; erythro-; Radnor; red; redskin; roan; robust; rooibos; Rotwelsch; rouge; roux; rowan; rubella; rubicund; rubric; ruby; ruddock; ruddy; rufous; Rufus; russet; rust.

It is the hypothetical source of/evidence for its existence is provided by: Latin ruber, also dialectal rufus "light red," mostly of hair; Greek erythros; Sanskrit rudhira-; Avestan raoidita-; Old Church Slavonic rudru, Polish rumiany, Russian rumjanyj "flushed, red," of complexions, etc.; Lithuanian raudas; Old Irish ruad, Welsh rhudd, Breton ruz "red."

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).