@pzack Why don't you post a link to the non-tab-delimited file?
If what you're saying turns out correct, than all you would need is to prefix each line with a repetition of the 1st word and a delimiter.
Sed could do that on Linux, any pattern-substitution in Perl, Python, Awk or Lua could do that.
You could even do it in Excel. First column your line, second column the
LEFT-function, third column a
concatenation of both column-values with a delimiter in between.