Where does “tilly” come from?

tilly (English) comes from Irish tuilleadh, from Old Irish tuilled, from Old Irish do·lína — increases, adds to.

tilly (English): An extra product given to a customer at no...

Definitions

Step	Language	Word	Meaning
1	Irish	tuilleadh	adding to, increasing; addition, increase; more;...
2	Old Irish	tuilled	increasing, adding to; increase, additional...
3	Old Irish	do·lína	increases, adds to