Easton's 1897 Bible Dictionary:

Pithom
   Egyptian, Pa-Tum, "house of Tum," the sun-god, one of the
   "treasure" cities built for Pharaoh Rameses II. by the
   Israelites (Ex. 1:11). It was probably the Patumos of the Greek
   historian Herodotus. It has now been satisfactorily identified
   with Tell-el-Maskhuta, about 12 miles west of Ismailia, and 20
   east of Tel-el-Kebir, on the southern bank of the present Suez
   Canal. Here have recently (1883) been discovered the ruins of
   supposed grain-chambers, and other evidences to show that this
   was a great "store city." Its immense ruin-heaps show that it
   was built of bricks, and partly also of bricks without straw.
   Succoth (Ex. 12:37) is supposed by some to be the secular name
   of this city, Pithom being its sacred name. This was the first
   halting-place of the Israelites in their exodus. It has been
   argued (Dr. Lansing) that these "store" cities "were residence
   cities, royal dwellings, such as the Pharaohs of old, the Kings
   of Israel, and our modern Khedives have ever loved to build,
   thus giving employment to the superabundant muscle of their
   enslaved peoples, and making a name for themselves."


Hitchcock's Bible Names Dictionary (late 1800's):

Pithom, their mouthful; a dilatation of the mouth