But anything used here will need to be documented as to time of use, as time periods are not given for each term
SENA Appendix C shows Manx Gaelic in the same language group as Oghamic Irish in "early period" (pre-1100), and compatible with English/Welsh. It also shows Manx Gaelic in the same language group as Middle Irish Gaelic and Early Modern Irish Gaelic in "late period" (1100-1600), also compatible with English/Welsh.
I'm sure this was already known, but just in case anyone was wondering.
"English surnames : their sources and significations (1875)"
"Studies on uncompounded personal names in Old English (1919)"