My 'Granny' spoke both English and German and it may be there is some grounding in language and translations that creates a variance in the words we use. Indeed, Adam Sachs writes on Random House's The Mavens' Word of the Day:
The form wheelbarrel is an example of a folk etymology. A folk etymology is a modification of a word to associate it with a more common or easily understood word. For example, the word bridegroom was originally something like bridegome, the second element being the Old English word for 'man'. When "gome" fell out of use, "bridegome" was changed to "bridegroom" on the analogy of the common and familiar word "groom," which is at least a plausible substitute." He goes on to explain, "the "barrow" element is rare in modern English, and "barrel" makes some sense--the trough of a wheelbarrow does resemble the inside of a barrel--so the word was changed to "wheelbarrel." Though the correct "wheelbarrow" is so common that a lasting change is unlikely, the "wheelbarrel" form represents a historically common process."
In the end I judge that our reader wins! So as not to confuse the issue, we still need a wheelbarrow or a wheelbarrel...whichever you might wish to donate! (Now, is that one word or two?)
Thanks RM! Still smiling!