Put your hands together, cupped. Now consider the bowl shape you have created. How much would it hold? If you say a double handful, you will be right, but how much more interesting it would be to call it a gowpen instead.
Not that you are likely to hear the word much, nor should you expect many people to understand you. Its active use is now restricted to parts of Scotland — you might for example come across it in the old Scots’ proverb: “A hanfu’ o’ trade is worth a gowpen o’ gold” (even a little knowledge of a trade is worth a great deal of money).
Originally the word came from Old Norse and I’m told it still exists in some modern Scandinavian dialects. When it first came into Britain, probably with Viking settlers before the Norman Conquest, it seems to have referred to a single cupped hand, the idea of a double handful being indicated by gowpens. Some writers continued to distinguish between one and two cupped hands in this way almost down to modern times, though the word now seems to be used only in the singular to refer to both hands.
With anything Scots, the instinct is to fly to Sir Walter Scott, and he does not disappoint. This is from The Black Dwarf: “A bag was suspended in the mill for David Ritchie’s benefit; and those who were carrying home a melder of meal, seldom failed to add a gowpen to the alms-bag of the deformed cripple”.
If you’d like to be even more obscure, you might try yepsen, a related form that is recorded in various English dialects — it never seems to have been spelled the same way twice: ipson, espin, yaspin, and yepsintle, among others.