Carica papaya is a non-woody plant with palmate (hand-like) leaves bunched near the top of bare, seldom-branching trunks. Tree shown is very different. If there is a likelihood of it having popped up on its own, look around you for a possible parent tree. It may be several properties away, or your specimen have come in from some distance via topsoil or in the roots of another plant. Plants dispersed by birds can also be spread over miles in one go.

Not a volunteer, it was definitely planted by the previous owners. They had an interest in rare and odd things. I think I've narrowed it down to a Stenocarpus sinuatus (Firewheel Tree), an Australian native, with the help from one of the California Gardening Forum members. So far, that seems to be closest to what I am seeing. I've sent photos to my local tree nursery (Brigg's Tree Nursery in Vista, Calif), who are always ID'ing things for customers. They kind have a little competition between themselves to see who can most frequently ID unusual specimens, so it's "game on" over at Brigg's :-)

Patty S.