What's the meaning of the phrase 'Lovey-dovey'?
'Lovey-dovey' is an affectionate, somewhat childish, name for a sweetheart. More widely, the term is used to describe sentimentally loving behaviour.
What's the origin of the phrase 'Lovey-dovey'?
'Lovey-dovey' is one of those reduplicated phrases where both words contribute to the meaning - like happy-clappy or topsy-turvy. That is to say, both lovey and dovey mean something outside of this expression.
Lovey is self-explanatory. Dovey is a reference to a dove. This accords with other pet names commonly used in English which refer to birds - duck, duckie, chicken, chuckie, chickadee.
The expression 'lovey-dovey' was in general use by the 1880s but isn't the easiest of phrases to research in the usual language databases - lovey is a common word and dovey is a surname and the name of a town and a river in the UK.
Lovey began being used as a pet name in the 17th century, as in this example from The Second Book of Rabelais, 1653:
My tender peggie, my Codpiece darling, my bob and hit, my slipshoe-lovie.
'Lovey-dovey' originated in Britain in the 18th century. The earliest reference to lovey and dovey together that I've found is in a collection of stories entitled Wooden Bowl, 1767:
Pronounce they never will their [real] names, But Toll for Polly, Zimm for James; Chuck, Lovey, Dovey...
The above might be said to be a coincidence of the two words but the phrase itself is found a few years later, in Thomas Holcroft's comedy Duplicity, 1781:
Nay, but don't cry in earnest, lovidovey.
For the next hundred years or so 'lovey-dovey' was only used as a pet name. By the late 19th century it was well enough established in the language to become and adjective. Things began to be dome in a lovey-dovey way, as in this from the Alabama newspaper The Eufaula Daily Times, 1872:
The "hunkidori," "cream and sugar," "lovey dovey," "hootchy coochy" attitude towards each other...
For the most part of its existence in the language 'lovey-dovey' was just a name. It is now used rather disparagingly, to refer to behaviour that is overly sentimental.