Man pages matching name xmvacreatesimplepopupmenu in section 3:

XmVaCreateSimplePopupMenu.3.en	debian 10 / libmotif-dev
XmVaCreateSimplePopupMenu.3.en	debian 11 / libmotif-dev
XmVaCreateSimplePopupMenu.3.en	debian 12 / libmotif-dev