namesake n.

"word by which a person or thing is denoted," Old English nama, noma "name, reputation," from Proto-Germanic *naman- (source also of Old Saxon namo, Old Frisian nama, Old High German namo, German Name, Middle Dutch name, Dutch naam, Old Norse nafn, Gothic namo "name"), from PIE root *no-men- "name."

Meaning "a famous person" is from 1610s (man of name "man of distinction" is from c. 1400). Meaning "one's reputation, that which is commonly said of a person" is from c. 1300. As a modifier meaning "well-known," it is attested by 1938.

In the name of "in behalf of, by authority of," used in invocations, etc., is by late 14c. Name-day "the day sacred to the saint whose name a person bears" is by 1721. Name brand "product made by a well-known company" is from 1944. Name-dropper "person who seeks to impress others by mentioning well-known persons in a familiar way" is by 1947. Name-child, one named out of regard for another, is attested by 1830. The name of the game "the essential thing or quality" is from 1966; to have one's name in lights "be a famous performer" is by 1908.

"I don't realize yet how fortunate I am. It seems that I have been dreaming. When I see my name in lights in front of the theatre, I think, 'No. It isn't I.' " [Billie Burke interview in "The Theatre Magazine," Nov. 1908]

[purpose], Middle English sake "strife, discord, enmity, dispute; legal dispute; blame, sin, guilt;" from Old English sacu "a cause at law, crime, dispute, guilt," from Proto-Germanic *sako "affair, thing, charge, accusation" (source also of Old Norse sök "charge, lawsuit, effect, cause," Old Frisian seke "strife, dispute, matter, thing," Dutch zaak "lawsuit, cause, sake, thing," German Sache "thing, matter, affair, cause"), from PIE root *sag- "to investigate, seek out" (source also of Old English secan, Gothic sokjan "to seek;" see seek).

Much of the word's original meaning has been taken over by case (n.1) and cause (n.), and it survives largely in phrases for the sake of and for _______'s sake "out of consideration or regard for" a person or thing (c. 1200, as for God's sake, early 14c.), both those formations are said to be probably from Norse, as their like has not been found in Old English.

"anything kept or given to be kept for the sake of the giver; a token of friendship," 1790, from keep (v.) + sake (n.1); an unusual formation on model of namesake; thus an object kept for the sake of the giver. The word was used c. 1830s in titles of popular holiday gift books containing beautiful engravings and mediocre poetry. As an adjective by 1839.