Daniel Cassidy in his book, How The Irish Invented Slang, claims that the word bicker, meaning to argue, comes from the Irish word béicire, which means ‘a shouter, a person who shouts’.
As Cassidy admits, the word bicker goes back a very, very long way in English. It is found in Chaucer. This in itself suggests that it is not of Irish origin, as there was little Irish influence on the English language that far back. In fact, there is no evidence that the Irish word béicire existed back then, though the word béicc (a shout) did exist at that time and some earlier equivalent of béicire may well have existed. The word béicire is a poor match for bicker. It doesn’t sound like bicker (the word béicire sounds more like English baker). If we substitute the meaning of béicire into sentences using bicker, it is clear that the meaning is problematic:
The kids were [shouty person] in the back of the car all the way home.
Why do you two always have to [shouty person]?
There is absolutely no doubt that bicker, in the form biker, is found as early as the thirteenth century in English. The University of Michigan online Middle English Dictionary (an excellent resource for the history of English gives a number of examples of the use of the words biker and bikeren: http://quod.lib.umich.edu/m/med/.
As the excellent Online Etymological Dictionary says:
early 14c., bikere, “to skirmish, fight,” perhaps from Middle Dutch bicken “to slash, stab, attack,” + -er, Middle English frequentative suffix (as in blabber, hover, patter). Meaning “to quarrel, petulantly contend with words” is from mid-15c. where exactly it came from, though some of the dictionaries suggest a possible connection with a Dutch word bicken, meaning ‘to slash or attack’. Bicker is found in English texts from the 13th century in the form biker.
As usual, Cassidy doctored the information found in other sources to make his own claims seem more probable (or even possible). Here, he says that “Bicker is (inexplicably) said to be formed in English from Middle Dutch bicken, to slash.” Plainly, a Middle English word biker meaning to skirmish deriving from a Middle Dutch word bicken meaning to slash, stab or attack is considerably more explicable than a Middle English word for to skirmish deriving from an Irish Gaelic word for ‘a shouty person’.