Our sense of time is tuned to the everyday: you can’t see your children grow or mountains erode, for the very simple reason that life would be impossible if you could. Genealogy usually keeps a researcher’s nose firmly against this grindstone of the humdrum, and that’s one of its beauties; it is very hard to stray into geological time-scales and grand historical abstractions when you can see individuals and families flagrantly disobeying the laws of statistics before your very eyes. Just occasionally, however, something will poke out from the background that gives a sense of the scale of the invisible changes going on.
The surname “Costello” has more than 70 recorded variant spellings in the records of the past two centuries, from “Castolo” to “Custullo”, (see here) but it has a very precise origin. It was adopted in the 12th century by the children of Jocelyn de Angulo, son of Gilbert, one of the original Norman invaders. There is disagreement as to whether Osdealbhach, the forename at the root of the surname Mac Osdealbhaigh (phonetically “McOStealvy”), is a genuine Gaelic name itself, or a mangled Gaelicisation of ‘Jocelyn’, but there is no doubt at all that this individual was the origin of the modern surname.
In 1911, around 10,000 individuals in Ireland bore the surname Costello or a variant. A first reaction might be to congratulate Jocelyn on his fecundity, but of course, over 7 centuries, anything up to half-a-million individuals could be the 20-generation ancestors of someone living in 1911, so Jocelyn was only responsible for the surname, not all the genes. Even so, the sheer numbers connected to him both as descendants and co-ancestors give a dizzying glimpse of the complexity of our relatedness.
Nothing punctures your sense of being in charge of your own life quite as thoroughly as a stinking head-cold – I have one at the moment – but genealogy can come a close second.