Wikipedia
Ubi sunt (literally "where are... [they]") is a phrase taken from the Latin Ubi sunt qui ante nos fuerunt?, meaning "Where are those who were before us?" Ubi nunc...? ("Where now?") is a common variant.
Sometimes interpreted to indicate nostalgia, the ubi sunt motif is actually a meditation on mortality and life's transience.
Ubi sunt is a phrase that begins several Latin medieval poems and occurs, for example, in the second stanza of the goliardic song " De Brevitate Vitae", known from its incipit as "Gaudeamus Igitur": "Ubi sunt qui ante nos / In mundo fuere?", "Where are those who, before us, existed in the world?" The theme was the common property of medieval Latin poets: Cicero may not have been available, but Boethius' line was known: Ubi nunc fidelis ossa Fabricii manent?