nostril (n.)

"one of the external openings of the nose, a nasal orifice," late 14c., nostrille, from Old English nosþyrl, nosðirl, literally "the hole of the nose," from nosu "nose" (from PIE root *nas- "nose") + þyrel "hole" (from PIE root *tere- (2) "cross over, pass through, overcome"). For metathesis of -r- and vowel, see wright. After the second element became obsolete as an independent, its form was corrupted in the compound.