Opsimath.

"A person who begins to learn or study late in life" — OED.

1808   Gentleman’s Mag. June 480/2   From the dissipation and idleness of his earlier years, Mr. Fox in Greek and Roman Literature was necessarily an Opsimath....
1968   T. M. Disch Camp Concentration (1969) i. 58   ‘Opsi?’ I asked Mordecai. ‘Short for opsimath—one who begins to learn late in life. We're all opsimaths here.’
1992   W. F. Buckley WindFall xvii. 268   They took me thirty years to learn, opsimath that I am in so many matters....

This is a word I learned only because it came up in a NYT acrostic — "Late learner, like Grandma Moses." I searched the entire archive of the NYT and found not a single appearance of this word. Surely, it's a bit useful.

1. It's funny, like oopsy-daisy.

2. You might be a polysyllabic show-off like William F. Buckley.

3. You could be Thomas M. Disch, writing "Camp Concentration." I read that book (almost half a century ago (it came out in 1968)).

In this chillingly plausible work of speculative fiction, Thomas M. Disch imagines an alternate 1970s in which America has declared war on the rest of the world and much of its own citizenry and is willing to use any weapon to assure victory.  Louis Sacchetti, a poet imprisoned for draft resistance, is delivered to a secret facility called Camp Archimedes, where he is the unwilling witness to the army's conscienceless experiments in “intelligence maximization.” In the experiment, Prisoners are given Pallidine, a drug derived from the syphilis spirochete, and their mental abilities quickly rise to the level of genius.  Unfortunately, a side effect of Pallidine is death.

Is there something I can learn from rereading this thing now that I've arrived in opsimath territory?

I crouched low, and the white rabbit hopped two hops closer, sniffed perspicaciously, raised itself on its hind feet, and extended its right forepaw, which I took between thumb and forefinger to shake.

“How do you do, Opsi,” I said.

Opsi withdrew his furry paw from my grasp and backed off.

“Opsi?” I asked Mordecai. “Short for opsimath— one who begins to learn late in life. We’re all opsimaths here. Now Mopsi, it’s your turn.”

The second rabbit, speckled brown and black, advanced. When it had reared itself on its hind legs I could see what appeared to be udders on its underbelly, though of quite disproportionate size. I pointed these out to M.

“It’s the orchitis, you know— inflammation of the testicles. That’s the price they pay for being so bright.” 

Opsimath— one who begins to learn late in life.... orchitis, you know— inflammation of the testicles.... It's like the book is teaching vocabulary words in alphabetical order.