"I' pathaît tch'il avait liu lé P'tit Albèrt, et i' s'mêlit!" - it seems he'd read the P'tit Albèrt and was bewitched. As part of the witch beliefs in Jersey, les mauvais livres (the bad books) were used by witches to cast spells. There were two main books: lé Grand Albèrt, ascribed to the authorship of Albertus Magnus, and lé P'tit Albèrt (a shorter version ascribed to Albert of Saxony). They circulated in France in the C18th and C19th, and in this way spread to the Channel Islands.
There was a suspicion that the literate were tempted to read forbidden knowledge and the word grammar travelled via French into English as grimoire (an occult book). Another version of the word grammar travelled via Scots into English as glamour (firstly in the meaning of a spell or enchantment).
The grimoire "lé Grand Albèrt" became known in Jèrriais as lé Grand-Mêle or lé Grand-Mêlé (another variation of grammar, reinterpreted as something big one got mixed up in - or shouldn't mix with).
S'mêler - to mix oneself, to get mixed up with - developed, through its association with the folk etymology of Grand-Mêle, the extra meaning of to be bewitched.
Logically enough, if the Grand Albèrt was lé Grand-Mêle, its shorter counterpart the Petit Albert became lé P'tit-Mêle (something small one got mixed up in), a further alteration from grammar.
One could refer to someone as knowing the Grand Albèrt by heart: i' sait l'grand albèrt par tchoeu - either because he knew too much or derisively as knowing nothing.