An Etymological Dictionary of Astronomy and Astrophysics

1. In at one end, side, or surface and out at the other.
   

2. From one to the other of; between or among the individual members or parts of.
   

3. Over the surface of, by way of, or within the limits or medium of.
   

4. During the whole period of (Dictionary.com).

Etymology (EN): M.E. (preposition and adv.), metathetic variant of thourgh, O.E. thurh, (cognates O.S. thuru, OFris. thruch, Du. door, O.H.G. thuruh, Ger. durch), cognate with Av. tarô, tarə “over, across, beyond,” L. trans-, → trans-.

Etymology (PE): Târu, related to tarâ-, → trans-, and from Av. tarô, tarə, as above.