What does "ioyning" mean?
Solution 1:
JEL already answered the question in the first comment. Since it's a question on definition, it probably won't hurt just to cite the dictionary of that era as some source.
In the A Dictionarie of the French and English Tongues (1611) by Randle Cotgrave
ioinct: A ioynt, ioyning, closure; seame
ioindre: To ioyne, couple, … or combine together
Iointe: A ioynt; closure; ioyning; seame