The acronym (SAW) is found in various forms such as (SA), (SAWA) or (SAWAW). The acronym (SAW) stands for "Sallalahu Alaihi Wa-salam" - May God's praise and peace be upon him. This acronym is used after mentioning the name of Prophet Muhammed (SAW) specifically, and shows respect and reverence.
The basis for this respectful phrase is found in the Quran.
إِنَّ اللَّهَ وَمَلَائِكَتَهُ يُصَلُّونَ عَلَى النَّبِيِّ يَا أَيُّهَا الَّذِينَ آمَنُوا صَلُّوا عَلَيْهِ وَسَلِّمُوا تَسْلِيمًا
'Allah and His Angels send blessings on the Prophet; O you who believe! Send your blessings on him, and salute him with all respect.' (Quran: 33:56)
The Arabic form of the acronym (a single letter, saad, in brackets) is shown.