It is named Segah because the maqam starts on the third degree in relation to the "basic" "Magham" scale found in Rast.
This is the third mode and consists of 0.5-1-1 tone which is created in amalgamation of three tetra-chords with the reach method.
Segah mugam associated with love, romantic feelings at listener.
[1] Subgenres of Segah includes: egah Zabul-Segah-Bardasht, Maye, Muya, Manandi-Mukhalif, Segah, high-pitched tone Zabul, Manandi-Hisar (in high-pitched tone), Manandi-Mukhalif (in high-pitched tone), Ashig-Kush, Mubarriga, Zabul, space for Segah, Kharij Segah-Bardasht, Maye, Takhtigah, Mubarriga, Manandi-Hisar, Manandi-Mukhalif, high-pitched tone Segah, space for Kharij Segah.
Middle eastern Sephardic Jews make heavy use of this in their liturgy.