The first element of this English place-name is unlikely to be a surname, despite the forms in -s- (2–7), as Stream is not recorded among the Anglo-Norman settlers either in Wexford or elsewhere in Ireland. The name probably refers to the streams that converge at the northeastern corner of this townland.

Streamstown is the name of a number of townlands elsewhere. Some are of English origin, while others such as Streamstown in Offaly are demonstrably translations of Irish Baile an tSrutháin or similar (see logainm.ie). The Irish form of the place-name proposed here is a translation, using the commonly occurring Irish name.

[It has recently been suggested that ‘...Ekwall’s dictionary of English place-names [The concise Oxford dictionary of English place-names] confirms ... Streamstown is not an English place-name. The ON straumr means a rapid stream/tideway, i.e. where tidal waters run rapidly inland along a stream (...)’ The methodology leading to such a conclusion is problematic in the extreme. The absence of an English-language place-name from a dictionary of place-names in England cannot be taken to preclude English-language origin for the same name in Ireland. Such an approach would be akin to suggesting that Barrystown (#53935) in the parish of Bannow, which derives its name from an Anglo-Norman surname, cannot be of English-language origin because no similar place-name occurs in England (see also Logainmneacha na hÉireann IV: Townland Names of County Wexford pp.522–3). Both stream and town were, and still are, productive words in the English of Ireland, and their occurrence in the present place-name is entirely unproblematic. Evidence of the productive usage of Eng. stream is found in the early seventeenth-century translations ‘Streamestowne’ and ‘Stremston’, the colonists’ new names for two places in Offaly known in Irish as Baile an tSrutháin (#41426; #41175) — one of which is situated at the foot of Slievebloom, far from tidal waters. There are also numerous later examples of Streamstown used to translate Baile an tSrutháin elsewhere in the country (e.g. #19460; #19680; #32563; #36155; #45099). Streamstown was also used as an English pseudo-translation of Barr an tSrutha (#18114) “the top, head of the stream, current” in County Galway.]

[Excerpt from Logainmneacha na hÉireann IV: Townland Names of County Wexford, 2016]