As late as mid-September 1921 Joyce added a second, slightly cryptic line to this sub-headline, in which speedpills is equated to “velocitous aeroliths” = speedy meteorites.
It would be tempting to think that he came across the word speedpill at the very last moment, spotting it by chance in one of the earliest adult baseball fiction books, the short-story collection Hearts and the Diamond (1921) by Gerald Beaumont, one of whose stories bears the title “The Speed Pill”, a reference to its hero Clyde Brennan (p. 187):
The split-second hand stood at 13.4.
Bob Connelly whistled. "A speed pill," he said, "Just a natural-born base-runner."
But there were significantly earlier occurrences of the term in other senses. At first it seems to be used jocularly and literally as a name for a speed-inducing drug for race horses:
Bedwell owes his success to his knowledge of drugs. This does not mean that he is familiar with the "speed pill", but that he knows how to get a horse in proper shape and keep him on edge until all that is required of him has been achieved.
"New Turf Wizard Free with Tonics", in Duluth (Minnesota) News Tribune (1909), 25 July p. 4
Two years later we witness the transition from a literal pill to a metaphorical one on the baseball field:
It took Dr. Walter Johnson and his speed pills to check the clouting fever that has been raging in the camp of the Athletes ever since Tuesday. After seeing the grass at Shibe Park wiped up with the mangled remains of his star pitchers for three successive afternoons, Jimmy McMeer yesterday afternoon trotted out his one best bet in the tall person of the aforesaid Dr.Walter Johnson, and Walter administered his justly celebrated speed pills with such good effect that the home folks were only saved the ignominy of a shutout by a mere detail, the detail being a husky wallop by Frank Baker in the second inning […]
Philadelphia Inquirer (1911), 29 April p. 10
The word pill, however, had been used as a synonym for "ball" since at least 1896, according to the OED, and found its way into baseball language around the turn of the century predating the chemical speed pill by a few years:
That careless youngster Zeckey Newmeyer strolled up to the plate and bumped a Hawley speed pill clear to the fence for a homerun.
Salt Lake Herald, August 4, 1901, p. 4
As the above quotations show the word seems to have had two meanings in relation to baseball. It could refer to a particularly fast base runner or to a "fastball", a particularly fast pitch.
There can be little doubt that the sub-headline in Ulysses uses the latter, as the plum stones that the two “ould ones” spit from the top of Nelson’s Pillar are turned into speed pills, velocitous aeroliths, fastballs:
They put the bag of plums between them and eat the plums out of it, one after another, wiping off with their handkerchiefs the plumjuice that dribbles out of their mouths and spitting the plumstones slowly out between the railings. (U 7.1024-27)
The journalistic hyperbole of headlinese also transforms Penelope into PEN THE CHAMP and the two harmless old women into FRISKY FRUMPS1.