Meaning of LA in English

LA

[la] interj [ME (northern dial.), fr. OE la] (bef. 12c) chiefly dial--used for emphasis or expressing surprise

[2]la n [ME, fr. ML, fr. the syllable sung to this note in a medieval hymn to St. John the Baptist] (14c): the 6th tone of the diatonic scale in solmization

Merriam-Webster English vocab.      Английский словарь Merriam Webster.