It’s been a while since anyone used this word, though you’ll find it in many older works. It means a bald-headed man or a person looked on with humorous contempt or mock pity.
Here’s a typical reference, from an eighteenth-century English translation of Gargantua and Pantagruel, by Rabelais:
After this, we e’en jogged to bed for that night; but the devil a bit poor pilgarlic could sleep one wink — the everlasting jingle-jangle of the bells kept me awake whether I would or no.
To speak of poor pilgarlic in terms of mock pity is typical of the word, whether you’re speaking about yourself, as here, or about somebody else.
Its origin is straightforward: it’s a compound of pil, a word that later changed its spelling to the modern peel, plus garlic. So it compares a man with a bald head to a peeled head of garlic.
But it wasn’t just a simple case of a ludicrous comparison; there was a strong hint about the reason why the man had gone bald — through an attack of the pox. So the contemptuous meaning arose, and was well established by the early seventeenth century. Later the link with venereal disease declined, but the adverse meaning survived.