"Frère Jacques" is a well-known children's song sung in the French language, usually used for basic melody training and practicing 'canon' music playing (where different players and/or singers start playing/singing the same tune with a temporal offset).
Jean-Luc Picard and the winners of the primary school science fair aboard the USS Enterprise-D sung this song while climbing up a turbolift shaft in 2368. (TNG: "Disaster")
"Frère Jacques" was one of the first tunes that Captain Picard, as Kamin, learned to play on his Ressikan flute. (TNG: "The Inner Light")
Picard (playing his Ressikan flute) and Nella Daren (playing her portable piano) performed a canon of "Frère Jacques" in Picard's quarters on the Enterprise-D in 2369. (TNG: "Lessons")
Lyrics
Original (French)
Frère Jacques,
Frère Jacques,
Dormez-vous?
Dormez-vous?
Sonnez les matines,
Sonnez les matines,
Dig, Ding, Dong!
Dig, Ding, Dong!
English translation
Are you sleeping?
Are you sleeping?
Brother John
Brother John
Morning bells are ringing,
Morning bells are ringing,
Ding, Ding, Dong!
Ding, Ding, Dong!