A threshold is piece of wood or stone that is beneath a door and serves as a boundary between indoors and outdoors. It is also used figuratively to mean a boundary or a line that is to be crossed. It is a very old word, dating back to Old English. The first element, thresh, originally meant to stamp on or trample and survives today in the verb to thresh (wheat) and in to thrash. The hold portion is of unknown origin. The threshold is literally the first place in a building you step.
The extended sense of a boundary or limit to be crossed actually appears earlier in the literature than the literal sense. The literal sense is certainly the original, but given the relative rarity of Old English manuscripts such reversals in dating are somewhat common when you go back this far. From Alfred’s c.888 translation of Boethius’ Consolation of Philosophy:
Se ilca [sc. Godes miht] forwyrnð þæræ sæ þæt heo ne mot þone þeorscwold oferstæppan þære eorþan.
(The same [i.e., God’s power] forewarns the sea that it may not overstep the threshold of the earth, but he has so fixed its limits, that it may not extend its boundary over the still earth.)
The literal sense can be found as far back as c.1000, but as mentioned is undoubtedly considerably older. From Ælfric’s translation of Exodus 12:22 from c.1000:
And dippað ysopan sceaft on þam blode, þe ys on þam þerxolde.
(And dip a spring of hyssop in the blood, that is on the threshold.)
There is a specious bit of internet lore, often going by the title ofLife in the 1500s, that badly misstates the origin of threshold. It claims that thresh was placed on the bare floor and a block of wood, the threshold, would keep the thresh in when the door was opened. The big problem is that there is no such thing as thresh. Thresh is not and never has been a noun. It is a verb meaning to beat, stamp, trample.
(Source: Oxford English Dictionary, 2nd Edition)
Copyright 1997-2014, by David Wilton