Messuage, in law, a term equivalent to a dwelling-house, and including outbuildings, orchard, curtilage or court-yard and garden. At one time "messuage" is supposed to have had a more extensive meaning than that comprised in the term "house", but such distinction, if it ever existed, no longer survives. -- Encyclopaedia Britannica, 11 ed., 1910-11.I have not been able to find a definition for accreditament. If I may be allowed a wild guess: "In a commercial sense credit is the promise to pay at a future time for valuable consideration in the present" --Enc. Brit. 3 ed. Perhaps, therefore, accreditaments denotes all the rents flowing to the title holder. I imagine an encyclopedia of law will describe "accreditament", but I haven't got one. It it helps in your further research, the transfer of property, and the modification of interests in relation to property, is in English law called "conveyancing".
PS. In modern deeds, the phrase "and all the appurtenances thereof" is sometimes appended to the list of items transferred. This American title deed from 1873, contains the following phrase:
Together with all and singular the ways, waters, water-courses, rights, liberties, privileges here accreditaments and appurtenances whatsoever thereunto belonging or in any use appertaining and the reversions and remainders, rents, issues and profits thereof and all the Estate...If the American legal vocabulary in 1873 was still close to the English/Canadian one of the 1840's, and if the usual legal habit of redundancy ("to have and to hold", etc.) is what's happening here, then accreditaments are not rents, but appurtenances, that is, according to the Enc. Brit. 11 ed.:
appurtenances, a legal term for what belongs to and goes with something else, the accessories or things usually conjoined with the substantive matter in question.Again, good luck to you.