Rogers Cadenhead wrote about POJOs ("Plain Old Java Objects"):
I added a comment about some possibly etymological factors. Reproduced here:
Etymology: at The Phone Company (back when it was "The"), they made a distinction between the way phones used to work (copper wires; basic calling services) versus the newer services (like Call Waiting, or Three-Way Conference calls) and the newer wireless transport technologies. The former were called "Plain Old Telephone Service", or POTS.
Now, fast forward to the C++ standards meetings, where the need arose to distinguish between data structures of the sort that could possibly be compatible with C, versus the newer C++ data structures that required all sorts of hidden language extras. What to call the former? Well, guess where Bjarne Stroustrup and Andrew Koenig worked at the time: Bell Labs. The slang POTS so perfectly fit this application, that they used "PODS" ... "Plain Old Data Structures". This was in common use within the committee while I was still attending meetings. That places it no later than 1995.
I think the term even made it into the C++ standard somewhere.
It certainly seems to me that this is where POJO came from, though I haven't traced down the coinage.