An Etymological Dictionary of Astronomy and Astrophysics

1. (v.tr.) To make wider or larger; cause to expand.
   
2. (v.intr.) To spread out; expand.

Etymology (EN): M.E. dilaten, from O.Fr. dilater,
from L. dilatare “make wider, enlarge,” from → dis- “apart” + latus “wide,” → latitude.

Etymology (PE): Farâxândan, farâxidan, infinitive from farâx “broad, wide, spacious;” Mid.Pers. frâxv, fraxv “broad, wide,” frâxvitan, frâxvênitan “to spread.”