Jonnie Robinson, Curator, English accents and dialects, British Library Sound Archive, writes:
Baby-talk, a feature of all languages, is an attempt by adult speakers to engage an infant in an attempt to provoke a response. We often use very simplified language and use plosive sounds that have a particularly strong acoustic effect, such as boo or bubble, and invent nonsense words with sounds that rely on repetition, such as cutchy-cutchy-coo - a sound that's not that dissimilar to the Portuguese word kikesh that Rui says he used to use. In fact the "b" sound is one of the first sounds babies use regardless of the mother tongue of their parents. At the babbling stage when babies are playing with sound in the early stages of acquiring language, most research suggests that all over the world, the sounds "b, m, p" are acquired very early on. It's no surprise then that numerous languages, like English, have words relating to infancy that feature a babble-like repetition of these sounds, such as baby, mama, papa.
There are several forms of address used in different dialects of English. Man is widely used in the north-east of England and indeed in Jamaican English. Pet is a typical north-eastern term of affection generally directed at women or children and popularised in the title of the television programme, Auf Wiedersehen, Pet and duck is used by speakers in a large area of the East Midlands. In many parts of Yorkshire and the north-east Midlands, even in conversations between absolute strangers, an older speaker is liable to address a younger speaker as flower, as once popularised by the comedian Charlie Williams, or even more commonly love, which can seem a little intimate, particularly perhaps to non-native speakers as Cecilia concedes. As Rui explains, these forms of address are actually redundant in terms of meaning, but are merely a natural reflex intended to create a favourable impression or an atmosphere of familiarity among speakers.