A compound of head + span
Proto-Indo-European *kap- ‘head’
…
Proto-Germanic *haubudą ‘head’
Proto-West Germanic *haubud
Old English hēafod ‘head’
Middle English heed ‘head’
English head
Proto-Indo-European *(s)pend- ‘to stretch’
Proto-Germanic *spannō ‘span, handbreadth’
Old English spann
Middle English spanne ‘a span’
English span
Today it means
noun A support for overhead power lines on a railway, consisting of two towers on either side of a railway connected by cables.
Language periods are conventional ranges, not dates for this word.
Etymograph / headspan
Shirt and support for this word