المؤخر
كلمة (المؤخِّر) في اللغة اسم فاعل من التأخير، وهو نقيض التقديم،...
Performing the voluntary prayer after the "Tarāweeh" (voluntary prayer performed after the ‘Ishā’ in Ramadan).
"Ta‘qeeb": delaying something and doing it after something else. It means following a deed with another one. The night "‘aqaba" the morning and the morning "‘aqaba" the night means that one of them followed the other.
Stating in the right order, without gap or separation between the joined parts. This is the meaning of the conjunction ‘fa’.