Its all in the latin roots, ten relates to ownership or holding a position, as in tenancy or US marines holding their ‘ten’.
So extend means to add to what you already hold and unextend means to return to where you already were.
Unlike retract which means to move back over ground you have already covered.
Anyhoo the point of contact is the greeks and also the point of contact between where you started out from and where you got to.
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