Saspeirs and Syspiritis from Greek sources are frequently linked with historic Sper ( modern town Ispir in Erzerum province ). However the scrupulous analysis of ancient texts shows that the two terms can't have the same location.
The location of Saspeir/Saspiri is described as a place between Colchians and Medes by Herodotus, who by the way is the only source who use that form. Based on that location it is virtually impossible to imagine a location in modern Ispir for Saspeir. In another post we provide multiple arguments for a theory which places Saspeir in eastern Georgia being in most likelihood the source of the term Iberia. The intermediate terms attested between Saspeir and Iberia are the Sapirs and Apeirs.
As for Syspiritis its location is explicitly mentioned near the Acilisene (modern Erzincan) which means that its connection with Sper/Ispir is secure.
The transformation of Syspiritis to Sper requires an explanation.
In a personal correspondace with reknown linguist Hrach Martirosyan proposed a plausible explanation to this shift. The Armenian language transformed the IE sibilants *s>h and then removed most of them. This is not specific to Armenian but has occurred in Greek and Iranian languages also. For example the European number six became hex in Greek while the Sanskrit sauma ( a drink ) became hauma in Iranian. In Armenian language the resulting h has tendency to drop in initial positions except before consonants like p or t.
Based on this phonetic shift the term Syspir will first start to sound in Armenian something like *susper then will shift into *husper. The second [s] will not shift to [h] because it had consonant like p ( also t ) after him.
But this form *husper also will not last long and the initial hu- will drop and only Sper will remain. This dropping of initial laryngeals h is also well known.
Strabo mentions a place known as Hyspiratis. Scholars believe that it is the same as the Syspiritis (=Sper). So why would Strabo use two different forms to denote a same place in the same text. Some proposed that its an orthographic error. However there is a notable difference between two mentions. Syspiritis is mentioned when discussing old Jason's Argonauts period while the form Hyspiratis is mentioned in the younger context of Alexander Macedonian conquests. In most likelihood between this periods local Armenian speakers had transformed the term into Husper which is reflected in the Strabo's texts.
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0239%3Abook%3D11%3Achapter%3D14#note14
