memorable adj.

Proto-Indo-European root meaning "to remember." 

It forms all or part of: commemorate; commemoration; mourn; memo; memoir; memorable; memorandum; memorial; memorious; memorize; memory; remember.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit smarati "remembers;" Avestan mimara "mindful;" Greek merimna "care, thought," mermeros "causing anxiety, mischievous, baneful;" Latin memoria "memory, remembrance, faculty of remembering," memor "mindful, remembering;" Serbo-Croatian mariti "to care for;" Welsh marth "sadness, anxiety;" Old Norse Mimir, name of the giant who guards the Well of Wisdom; Old English gemimor "known," murnan "to mourn, remember sorrowfully;" Dutch mijmeren "to ponder."

"not memorable," 1550s, from Latin immemorabilis "not worth mentioning; silent," from assimilated form of in- "not" (see in- (1)) + memorabilis (see memorable). In English it occasionally has been used to mean "old beyond memory," but that sense is best left to immemorial.