The word cross is recorded in 10th-century Old English as cros, exclusively for the instrument of Christ's crucifixion, replacing the native Old English word rood. The word's history is complicated; it appears to have entered English from Old Irish, possibly via Old Norse, ultimately from the Latin crux (or its accusative crucem and its genitive crucis), "stake, cross". The English verb to cross arises from the noun c. 1200, first in the sense "to make the sign of the cross"; the generic meaning "to intersect" develops in the 15th century.
The Latin word was, however, influenced by popular etymology by a native Germanic word reconstructed as *krukjo (English crook, Old English crycce, Old Norse krokr, Old High German krucka). This word, by conflation with Latin crux, gave rise to Old French crocier (modern French crosse), the term for a shepherd's crook, adopted in English as crosier.
Latin crux referred to the gibbet where criminals were executed, a stake or pole, with or without transom, on which the condemned were impaled or hanged, but more particularly a cross or the pole of a carriage. From this word was derived the Latin verb crucio "to put to death on the cross" or (more frequently) "to put to the rack, to torture, torment" especially in reference to mental troubles. The field of etymology is of no help in any effort to trace a supposed original meaning of crux. A crux can be of various shapes: from a single beam used for impaling or suspending (crux simplex) to the various composite kinds of cross (crux compacta) made from more beams than one. The latter shapes include not only the traditional †-shaped cross (the crux immissa), but also the T-shaped cross (the crux commissa or Tau Cross), which the Early Christian descriptions of the execution cross indicate as the normal form in use at that time, and the X-shaped cross (the crux decussata or saltire).
The Greek equivalent of Latin crux "stake, gibbet" is σταυρός stauros, found in texts of four centuries or more before the gospels and always in the plural number to indicate a stake or pole. From the first century BC it is used to indicate an instrument used in executions. The Greek word is used in Early Christian descriptions of the execution cross, which indicate that its normal shape was similar to the Greek letter tau (Τ).