Probably alteration of French taïaut (interjection used in deer-hunting), from Middle French tahou, tayo, from Old French taho, ta ho, tielau (interjection given to hounds to return), composed of ta (particle used to prod animals) + ho ! (“halt!, hold!”). More at ho.
- (UK) used to urge on a fox hunt, especially when the fox is sighted.
- There he is! Coming out of that coppice! Tallyho tallyho tallyho!
- a simple greeting, exclusively used by the upper classes.
- Tallyho chaps! What's the time, anybody?
See also 
tallyho (plural tallyhos)
- the interjection.
- Alright, I'll give them the old tallyho.
- to articulate the interjection.
- I'll tallyho once we've got to the top.