> Can anyone help me out in finding about the remote origins of the
> english/german verbs do/tun?.
It's a very wide-spread Indo-European root, *dheh1. It appears with
reduplication in Sanskrit (dadha:mi) and Greek (tithe:mi) and in both
languages also in forms without the reduplication. In Latin the initial
#dh- appears by a regular sound change as an f-, so the root is hidden in
the word facio (no firm explanation for the -c-) and it also appears in
compounds as -do, as in credo, abdo, condo, perdo, but there could well be
contamination from the "give" root *deh3.
It is also attested in Armenian, Phrygian, Messapic, OCS, Hittite,
Tocharian and Lycian
It is very productive, with various noun and adjective forms.
Hope that gives you enough information.
Peter