Answers on this question conclude that "portion" refers to inheritance. Just before Elijah is taken to Heaven, Elisha asks for a "double portion" of his spirit.
2 Kings 2:9 When they had crossed over, Elijah said to Elisha, “What can I do for you, before I am taken away from you?” Elisha answered, “May I receive a double portion of the prophetic spirit that energizes you.” 2:10 Elijah replied, “That’s a difficult request! If you see me taken from you, may it be so, but if you don’t, it will not happen.” [NET]
However, this passage does not use either word from the answer. Instead, it uses "peh" in the phrase פִּֽי־שְׁנַיִם pi-shnayim. שְׁנַיִם( shnayim means double.) Peh is used in such a sense (portion) also in Deuteronomy 21:17, where the same phrase occurs, פִּי שְׁנַיִם pi shnayim.
Deuteronomy 21:17 Rather, he must acknowledge the son of the less loved wife as firstborn and give him the double portion of all he has, for that son is the beginning of his father’s procreative power – to him should go the right of the firstborn. [NET]
As there is no other prophet associated with Elijah, what does it mean for Elisha to receive Elijah's double portion?
Pi is translated as "portion" only twice in the KJV. However, a related word appears in 1 Samuel 13:21 (pim). (Both pi and pim are pronounced with long-e vowel sounds.)
13:21 They charged two-thirds of a shekel to sharpen plowshares and cutting instruments, and a third of a shekel to sharpen picks and axes, and to set ox goads.
The NET translators argue for pim meaning "two thirds of a shekel" based on archeology finds of stones marked pim which weigh, on average, 0.268 ounces, about two thirds of a shekel. See P. K. McCarter, I Samuel (AB), 238; DNWSI 2:910; and G. I. Davies, Ancient Hebrew Inscriptions, 259.