Who was Matilda in the song “Waltzing Matilda”?

In the Australian song “Waltzing Matilda,” a billabong is a pool of stag-
nant water. A swagman was someone who carried around everything he
owned in a knapsack. Waltzing meant hiking, and Matilda wasn’t a
woman but rather an Australian word for a knapsack. So Waltzing
Matilda means: walking with my knapsack.