mocking of affected gentility, 1874, in derisive imitation of "swell" way of talking.
A phrase used to mean the equivalent of ''It doesn't matter'': You're canceling our date? Oh well, lah-di-dah (1970s+)
A dandyish or sissified man; superrefined and delicate person: Some lah-de-dah with a cane (1883+)
To treat in a nonchalant, offhand manner: The outfielder la-di-da'd the catch (1970s+)
[an imitation of casual and aristocratic speech]