The Latin word, canonicus, means belonging to (religious) canon...ie the rules of the Church of England...or belonging to the order of canons, the latter being clergymen. Canonicorum looks to me to be the genitive plural, so I'd guess it means "of the church's rules" or "of the relevant clergymen". Perhaps if you provide a context, some greater expert will be able to provide a more accurate response.
It's usually encountered as part of a place name eg Whitchurch Canonicorum in Dorset. Here the canons are clergy of Salisbury Cathedral and produce of the area used to provide their income.