. The name of the river likely has Brittonic origins, influenced in its evolution by later interest in the Egyptian goddess
Isis. Known name variants for the upper Thames, recorded during the
medieval period, include Ysa or Usa (14th century), Isa, Ise (14th century), and Isis or Ouse (16th century). The name variants
Isa,
Ise, suggest a Celtic origin and may derive from
Brittonic is ('refresh') or
isca ('water'). Many common river names have a similar origin, including the
Axe,
Esk,
Exe and
Usk, as well as the Celtic name for the
Danube,
Istros. It is possible that the earlier name
Isa had a different meaning that was lost when replaced by a similar sounding name. It is unlikely that these early names were related to the Egyptian goddess. The association between Oxford and the Egyptian goddess
Isis might be explained by her role as
Stella Maris – "
Star of the Sea" and "divine protector of sailors and fishermen". The
Latin Stella Maris relates to
Mary, mother of Jesus, and the worship of
Isis was associated with the transformation of Roman society away from
paganism towards
Christianity. It had been conjectured that the Romano-British name for the Thames ("
Tamesis") is a
conflation (joining together) of its two main
tributary names, the
River Thame and the Isis. The conflation theory might explain why the Thames retained a trailing 's' – but the River Thame did not. The conflation theory was proposed and endorsed by
antiquarians and scholars during the
middle ages, including
Ranulf Higden,
John Leland, and
William Camden (1551–1623). In the late 17th century, the Welsh scholar
Edward Lhuyd – second Keeper of the
Ashmolean Museum in Oxford – endorsed the conflation theory in
Parochailia (1695). Use of the modern form of the name Isis for the river was first recorded c.1540, and may have been influenced by the
study of religion at the University of Oxford, the association of the Egyptian goddess with
Christianity, and the association of the Thames with the Egyptian goddess. It may also have been influenced by the revival of interest in classical Roman antiquities during the
Renaissance in the 16th century, and the conflation theory endorsed by the
antiquarian John Leland. ==Name legacy==