I have noted that the Brisbane family has originated by adopting the name of their property.
There is a possibility that the Caldwell family originated from the name of a property "Caldwell" in Renfrew.
Both families are supposed to have been in the train of the FitzAllan's when they came to Scotland.
Neither Brisbane nor Caldwell is a village or even a hamlet - they are landed properties of a single family (with normal retainer's etc).
The Brisbane property remained in the hands of the Brisbane family until sometimf in the 1800's (at least) the caldwell property paseed to the Mure family in the mid 1300's. This may not have had a great deal of bearing on the names which were probably established by this time.
Given normal fecundity and a somewhat similar starting point it is strange that the Caldwell's very obviously outnumber the Brisbane's by a vast amount.
This must reinforce my belief that Caldwell does not have the single source of being named after Caldwell, Renfrew.

A countervailing argument would be that the original Caldwell property was HUGE whilst the Brisbane property was relatively small. Consequently there were probably more retainers or fuedal dependents upon the Caldwell lands. This latter argument I could possibly accept but it would also mean that there were many Caldwell roots from the same area who would not have been necessarily blood related.

The Mures managed to carve out at least three substantial holdings from the original Caldwell Estate (with appropriately sized mansions): Caldwell itself, Cowdams, and Glanderston.