What does “yo-ho-ho” mean?

Accordin’ to yon pirate page, yo-ho-ho indeed be pirate laughter.

But there be also another source claimin’ that ’tis merely a scallywag’s variant of yo-heave-ho, the chant that all good sea-farin’ folk use to keep their rhythm when haulin’ cannon to the scuppers.

Seems ’tis likely yo-ho-ho be used to maintain the rhythm in yer fine sea chantey as well. When ye shipmates sing out yo, yer all be givin’ yon rope a hearty pull.

Yo-ho-ho is related to yoho, which is in the Oxford Dictionary of English:

An exclamation used to call attention: orig. in nautical use, hence generally; also sometimes used like yo-heave-ho int., q.v.

It dates from the 1700s:

1769 W. Falconer Universal Dict. Marine (1780) 11, Hola-ho, a cry which answers to yoe-hoe.

Yo ho ho may either have been extended to fit in the song, or an alternative version of yo heave ho or yoho.