|Suggested Meaning:||valley of the castle|
|Gaelic Gleann a’ Chaisteil ‘valley of the castle’|
|Blaeu Coila (1654):||No Entry|
|OS Name Books (1855-57):||Glenhastel|
|Location:||Ordnance Survey (1894)|
Gaelic gleann a’ chaisteil ‘valley of the castle’
Glenhastel Burn rises in Glenhastel Craigs and flows through Glenhastel on its way to meeting the Carcow Burn just north of Carcow farm (now known as Monquhill).
The Ordnance Survey Name Book (1855-57) entries for Glenhastel read –
Glenhastel: A hollow through which a stream of the same name flows.
Glenhastel Burn: A Stream rising at Glenhastel Craig and flowing in a NW. [North West] direction, unites with Carcow Burn, north of Blood Moss
Glenhastel Craigs: Precipitous rocks, situated at the source of Glenhastel Burn
In discussions with Michael Ansell he identified Glenhastel as Gaelic Gleann a’ Chaisteil ‘valley of the castle’ and noted the proximity with Carcow which might contain Cumbric caer ‘fort’. He also explained that on occasion the term caisteal was used figuratively so if there’s a hill or rocky top that looks somehow castellated that might explain it .
There is no record of a castle or fortification in this vicinity other than a reference to Covecastlehill near Carco  which possibly is a misreading of Covecasehill shown on John Thomson’s Atlas of Scotland (1828). The second element –casehill could possibly be an anglicisation of Gaelic chaistell . However, the name Covecasehill does not appear in earlier or later maps other than a later imprint of Thomson’s map and is not known locally.
Perhaps the craigs, rocks  at the source of Glenhastel Burn are the source of the name chaisteil.
N.B. Two miles to the east of Glenhastel Craigs in the upper reaches of Glen Afton is a rock named Castle William, albeit it is not castellated in form (see Map 4).
| Courtesy of Michael Ansell|
| George Sanderson, ‘New Cumnock Far and Away’ p. 39|
| Dictionaries of the Scots Language |craig|
|Reproduced with the permission of the National Library of Scotland|
|Map 1 | Ordnance Survey (1894) |Glenhastel|
|Map 2 | John Thomson’s Atlas of Scotland | Covecasehill|
|Map 3 | Ordnance Survey (1894) | Glenhastel Craigs|
|Map 4 | Ordnance Survey (1894) | Castle William|