extinct marine arthropod, 1820, from Modern Latin Trilobites (Walch, 1771), from Greek tri- "three" (see three) + lobos "lobe" (see lobe); so called because its body is divided into three lobes.
Entries linking to trilobite
three adj., n.
"1 more than two; the number which is one more than two; a symbol representing this number;" Old English þreo, fem. and neuter (masc. þri, þrie), from Proto-Germanic *thrijiz (source also of Old Saxon thria, Old Frisian thre, Middle Dutch and Dutch drie, Old High German dri, German drei, Old Norse þrir, Danish tre), from nominative plural of PIE root *trei- "three" (source also of Sanskrit trayas, Avestan thri, Greek treis, Latin tres, Lithuanian trys, Old Church Slavonic trye, Irish and Welsh tri "three").
3-D first attested 1952, abbreviation of three-dimensional (1878). Three-piece suit is recorded from 1909. Three cheers for ______ is recorded from 1751. Three-martini lunch is attested from 1972. Three-ring circus is recorded by 1898. Three-sixty "complete turnaround" is from 1927, originally among aviators, in reference to the number of degrees in a full circle. Three musketeers translates French les trois mousquetaires, title of the 1844 novel by Alexandre Dumas père.
lobe n.
early 15c., "a lobe of the liver or lungs," from Medieval Latin lobus "a lobe," from Late Latin lobus "hull, husk, pod," from Greek lobos "lobe, lap, slip; vegetable pod," used of lap- or slip-like parts of the body or plants, especially "earlobe," but also of lobes of the liver or lungs, a word of unknown origin. It is perhaps related to Greek leberis "husk of fruits," from PIE *logwos. Beekes writes that the proposed connection with the PIE source of English lap (n.1)) "is semantically attractive." Extended 1670s to divisions of the brain; 1889 to ice sheets. The common notion is "rounded protruding part."