BONHILL
Joseph Irving writing in 1879 refers to the author of Caledonia. This is probably Tacitus, the ancient Roman historian who wrote about Scotland. We cannot be sure of his accuracy, but it is worthwhile considering it.
According to the erudite author of the "Caledonia", this parish derives its name from the Gaelic word, Bog-n'-uill, or the "foot of the riverulet" - an entymology which is supported by the situation of the parish church. IN early charters the name is spelt "Bethelulle", "Bohtlul", and "Buchlul", but the Gaelic guttural becomes afterwards softened into Balul, and finally into its present form Bonhill....
....The earliest reference to this parish which has yet been discovered is in a charter granted in 1270 by Maldowen, the third Earl of Lennox, who, in that year, confirmed a grant for which Forveleth (supposed to be a grand-daughter of Alwyn, second Earl of Lennox) had made to the church of Glasgow of "the land of Hachenkeroch, into the parish of Buthelulle. [Irving].
This correlates with the description in Wikipedia.
The area is mentioned in a charter of 1225 giving the monks from Paisley Abbey fishing rights on the east bank of the River Leven at the Linbrane pool.Bonhill Parish was noted in a charter of 1270 as "the parish of Buthehille", and the name became Bonyle about 1550, with the variants Binnuill, Bonuil and Bonill appearing before Bonhill was adopted by 1700. In 1650 this small poor parish was enlarged, and since then the Parish has included most of the towns and villages in the Vale of Leven.
The village of Bonhill itself featured an early church, and a ford across the River Leven on the drovers' road to Glasgow. The first modern church was built close to the river in 1747, and it was replaced in 1835 by the present Church of Scotland building on the site of an earlier small church. Various churches of other denominations were constructed from 1830, but closed in the 1960s. [Wiki].
The Gazeteer for Scotland gives a more up to date description:
Situated on the east bank of the River Leven in West Dunabrtonshire opposite Alexandria and a mile (1.5 km) northeast of Renton, Bonhill is the oldest of the Vale of Leven villages which grew into a textile town known for bleaching and dyeing. Despite the decline of that industry, it grew rapidly again from the 1970s, with public housing built as part of the Glasgow Overspill project. Sometimes known as New Bonhill, this extension lies to the southeast of the original village and comprises the districts of Braehead, O'Hare, Ladyton, Nobleston, Pappert and Redburn.
Much of the old village has been demolished, although Bonhill Parish Church (1835) remains. It was well-known for its halfpenny toll bridge (1836) which was named the 'Bawbee Bridge'. Sir JamesSmollett, grandfather of the novelist Tobias Smollett (1721-71), was granted the lands of Bonhill in 1660. Other notable sons of Bonhill include entrepreneur Sir John Pender (1816 - 1896), Australian Refrigeration pioneer James Harrison (1816-93) and footballer Neilly McCallum (1869 - 1920).
Sir John Pender KCMG GCMG FSA FRSE (10 September 1816 – 7 July 1896) was a Scottish submarine communications cable pioneer and politician.
In this map of 1860 we see Bonhill as strung out along the main road.
A = Bonhill Bridge; B = Dalmonach Print Works: C = Church and burial ground: D = Bonhill Quarry; E = Ladytoun; F = Ladyton Cottage: G = Place of Bonhill across the river in Renton.
GAZETEER FOR SCOTLAND - Scottish Place Names : https://www.scottish-places.info/towns/townfirst441.html
IRVING, JOSEPH. The Book of Dumbartonshire. W. and A.K. Johnston. Edinburgh and London. 1879.
NATIONAL LIBRARY OF SCOTLAND : MAPS : Dumbartonshire, Sheet XVIII. Survey date: 1860, Publication date: 1864. https://maps.nls.uk/view/228777145
WIKIPEDIA : https://en.wikipedia.org/wiki/Bonhill