My Mother's father's surname is Cousins. I'm doing some research to find the origin and the meaning of the name.
The origin of a surname can only be determined by doing thorough research of that line of ancestry, to find the earliest spelling, location, and language. In many cases, there are several proposed origins for surnames. The case of Cousins seems to be relatively straightforward, since 'cousin' is an English word.
A 1901 Dictionary of English and Welsh Surnames gives the following etymology:
Cousen, Cousens, Cousins, Cousens, Cousin, Cussons, Cussen, Cossins, Cossin.—
Nick. 'the cousin,' a kinsman or near relative; M.E. cosin. The final s is patronymic, as in Jenkins, Williams, Jones, &c.
The Dictionary of American Family Names gives this fuller (and perhaps more fanciful) etymology:
English: patronymic from the nickname Cousin.
English and French: nickname from Middle English, Old French co(u)sin, cusin (Latin consobrinus), which in the Middle Ages, as in Shakespearean English, had the general meaning ‘relative’, ‘kinsman’. The surname would thus have denoted a person related in some way to a prominent figure in the neighborhood. In some cases it may also have been a nickname for someone who used the term ‘cousin’ frequently as a familiar term of address. The old slang word cozen ‘cheat’, perhaps derives from the medieval confidence trickster's use of the word cousin as a term of address to invoke a spurious familiarity. The patronymics constitute the most frequent forms of this name.