unthrift
A lack of thriftiness; prodigality.
countable, uncountable
Someone who is not thrifty; a spendthrift, someone who is not careful with their money.
archaic, countable, uncountable
For frantick faitours half mad and half ſtraught; But my learning is of another degree
My ſcoles are not for unthriftes untaught,
Where it comes from
From Middle English unthrift, equivalent to un- + thrift.
Adapted from the Wiktionary entry unthrift (CC BY-SA 4.0).