who was Egelina de Courtenay ??

Here's what MedLands has to say about the first Egelina:

[Daughter of Renaud de Courtenay and second wife Hawise d'Avranches - be careful, there are lots of Hawises in this time period!]

AIGELINE de Courtenay (-after 1219). The chronology dictates that Aigeline must have been her father’s daughter by his second marriage. "Gilebertus Basset" granted land at Bicester and other properties to the prior of Bicester, for the souls of "mee et uxoris mee Egeline et liberorum nostrorum", by charter dated to [1182/85], witnessed by "…Egelina uxore mea, Aliz Basset…Thoma Basset, Fulcone Basset…"[217]. King John confirmed the grant of "manerio suo de Strafford" to "Gilberto Basset et Eggelin uxori eius" by charter dated 21 Mar 1200[218]. The presence of Aigeline in the grant suggests that the property in question had previously been held by her family. A charter of King Edward II records that “Gilebertus Basset” founded Bicester priory, Oxfordshire, for the souls of "…uxoris meæ Egelinæ et liberorum nostrorum", witnessed by "uxore mea Egelina…"[219]. "Aquilina de Curt" donated "totam terram meam de Swthona" to Bicester priory, for the souls of "patris mei Reginaldi de Curt et…matris mee et…sponsi mei Gilleberti Basset et filii mei Thome Basset", by charter dated to [1205/06], witnessed by "Robert de [C]urt, Thoma Basset…"[220]. The Testa de Nevill includes a list of landholdings in Oxfordshire, dated 1219, which includes "Egelina de Curtenai" holding land "in Craumerse…hundredo de Langetroe…[et] in Burnecestre…in hundredo de Pockedelau"[221]. m GILBERT Basset [I], son of THOMAS Basset [I] of Headington, Oxfordshire & his wife Alice de Dunstanville (-[1205/06]).
http://fmg.ac/Projects/MedLands/chamsensjoi.htm#RenaudCourtenaydied...

Once the name got into the family, it could be reused in later generations.