What does it mean?
A tillicum is a person, but especially a friend. Mate, perhaps, might be the nearest equivalent used in England, but of course tillicum sounds much sillier.
Illustration by Walter Crane: Alphabet of Old Friends.
And what a lovely day to tell someone they're a proper tillicum.
Just make sure you have a head start before you do.
Word To Use Today: tillicum. This word comes from Chinook Jargon* from Chinook tixam, relations, people, or tribe, as distinguished from chiefs.
*As far as I know the only language to have started life at a dinner party.