Hi Norman,
Another suggestion is that the surname Connell could also have been McConnell. It was not unusual at the time for the "Mc" in surnames to be dropped or picked back up again.
Could be a complete red herring but worth pointing out to you for perhaps further investigation but.... there is a marriage in 1830 in Kilmarnock of a William McConnell to a Jean Hall.
https://familysearch.org/pal:/MM9.1.1/XT24-R2LThis marriage is also recorded at another Parish - St Quivox and Newton , Ayr
https://familysearch.org/pal:/MM9.1.1/XTNZ-H4PI believe this couple are on the 1841 Census and 1851 Census
1841- St Quivox, Ayrshire
Parish- Newton -upon- Ayr. Main Street
MCCONNEL William M 41 Shoemaker
MCCONNEL Jane F 33
MCCONNEL Francis M 5
MCCONNEL Jennet F 1
All are born in Ayrshire.
1851- Newton-upon- Ayr, Allison Street
MCCONNELL William Head M M 57 Shoemaker Ayrshire - Straiton
MCCONNELL Jean Wife M F 45 Sewer Ayrshire - Newton Upon Ayr(Originally: Ayrshire - Newton)
MCCONNELL Janet Dau U F 11 Ayrshire - Newton Upon Ayr(Originally: Ayrshire - Newton)
MCCONNELL William Son U M 5 Scholar Ayrshire - Monkton
MCCONNELL Margaret Dau U F 4 Ayrshire - Monkton
Further research would be required to establish that this couple is the William McConnell and Jean Hall who married in 1830 in Kilmarnock. But William, a shoemaker, is certainly old enough to be the father of William Connell born 1821.
All supposition, at this stage, of course
. And it could be a wildgoose chase, unfortunately.
Good luck,
Looby