Note: The Oxford English Dictionary, Third Edition, hypothesizes that this miter is the same word as miter entry 3, "perhaps with reference to the early form of the episcopal mitre, which had a vertical band bisecting the angle at the top." This is possible, though it is questionable how familiar a joiner or builder in the sixteenth or seventeenth century—assuming this period is when the word arose—would be with the construction of a bishop's hat. The word is also attested as French mitre with the identical meaning in the Encyclopédie of Denis Diderot, et al. (tome 10 [1765], p. 584), along with a description of a miter box (boîte de mitre). The information may have been drawn from the multivolume Descriptions des arts et métiers that appeared around the same time as the Encyclopédie and from which much of its technical information was derived. The Oxford English Dictionary also notes the occurrence of Latin mitra in the Dictionary of Medieval Latin from British Sources, though the assignment of the meaning "miter square" to the citation in question appears to be conjectural.

Note: Greek mítra has been compared with Sanskrit mitráḥ "partner in a treaty or pact, friend," Mitráḥ, the name of a deity, mitrám "contract, treaty, friendship," and Avestan miθra- "treaty, contract." Hypothetically, these could be the outcomes of an Indo-European noun *mi-tro- "connection, attachment," a derivative of a presumed verbal base *mei̯- "connect, join," as both the Greek and Indo-Iranian nouns might describe something connected, literally in the case of the Greek word, figuratively in the Indo-Iranian case. However, there appears to be no certain evidence for a verb *mei̯- with this meaning, as Sanskrit minóti "(s/he) fixes, erects, establishes" mita- "fixed, erected," Old Irish do·dímen "(s/he) binds, makes fast, fixes," point to a somewhat different sense. Alternatively, Greek mítra has been taken as a borrowing from Indo-Iranian—improbably, given attestation in Homer—or a borrowing from an Asian or substratum language.