interwiki_putfirst_doubled was introduced in March 2005 (5bc8ca0ad) defined as
Languages in interwiki_putfirst_doubled get their languages that are put first will be given again in the 'normal' list.
And then revised a bit in July 2005 (530ad688e) to be
Languages in interwiki_putfirst_doubled should have a number plus a list of languages. If there are at least the number of interwiki links, all languages in the list should be placed at the front as well as in the normal list.
It was last used Dec 2005 (3662bc3b6).