Thanks, Ian; I certainly hadn't made that connection.  The evolution of Cailin o cois tSiure me has been a convoluted one, and the earliest examples bear little resemblance to the tune we are familiar with; to the extent, indeed, that several Croppy Boy tunes are treated as effectively separate, and for all I know may not be related to each other.

There was some discussion of Callino Casturame, (the title under which it was first published), in this old thread:  Callino Casturame,  and Bruce Olson goes into considerable detail in the "Additional Tunes and Histories" file at his website:  Callino Casturame, alias, In summer time.

Entries at  The Fiddler's Companion  may also be helpful:

The Croppy Boy

Those entries contain some tune examples in abc format, and others can be found at  J C's Tunefinder  for comparison.