We don't have synonyms for primmer yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are primer, trimmer and rimmer.
(n) :
Obsolete form of primer (“children's teaching book”). [(historical, Catholicism ecclesiastical) A prayer or devotional book intended for laity, initially an abridgment of the breviary and manual including the hours of the Virgin Mary, 15 gradual and 7 penitential psalms, the litany, the placebo and dirige forming the office of the dead, and the commendations.]
(n) :
Obsolete form of primer (“children's teaching book”). [(historical, Catholicism ecclesiastical) A prayer or devotional book intended for laity, initially an abridgment of the breviary and manual including the hours of the Virgin Mary, 15 gradual and 7 penitential psalms, the litany, the placebo and dirige forming the office of the dead, and the commendations.]