According to The Big Dictionary*
handsel n. & v. (also hansel) archaic
n. 1. a gift at the beginning of the new year, or on coming into new circumstances …
v. tr. 1. … give a handsel to …
[Middle English, corresponding to Old English handselen 'giving into a person's hands', Old Norse handsal 'giving of hte hand (esp in promise)' ...
But that's not the meaning I know for it. I don't know if hanseling is just a Scots thing. The only people I know who do are my family, who are all Scottish. I don't know if anyone else does it. Our tradition (superstition?) goes like this. If you give someone a gift of something to put money in (a purse or wallet) or of something sharp (eg a knife, scissors or a brooch) you must always 'hansel' the gift, meaning a gift of a silver coin accompanies it.
For a purse or wallet, you put the coin inside, so that the person's purse will never be empty. For a sharp object, you give the coin at the same time you give the gift, so that your friendship is not cut or pierced.
And this explains why my mum turned around and drove back to my house last week to give me a five pence piece. On her way home she realised she'd forgotten to hansel the beautiful shawl pin she'd bought me for my birthday (normally she'd've included it in the box when wrapping the gift but we'd been to the shops together to look for a pin and so she hadn't wrapped it).
This is the brooch in situ on my north sea shawl. I think it must be the only penannular-style brooch available in Manchester (certainly felt that way after we'd trawled the shops. I hate shopping. I do not look on it as a leisure activity, unlike some of my family [hello sis]).
*The Concise Oxford Dictionary of Current English 9th edition, 1995. The biggest dictionary we have in our house (and ultimate arbiter of Scrabble disputes) until I win the lottery and buy the complete OED.