It would seem that Shakespeare made the most of the popular phrases of his day along with adding a few of his own and “budge an inch” is no exception.
There are records of the inch as a unit measure being used circa AD 1000 (both Laws of Æthelberht and Laws of Ælfred). Dating from the first half of the 10th century, the term “inch” is found in the Laws of Hywel Dda and was recorded in “Ancient Laws and Institutes of Wales” (vol i., pp. 184,187,189). The definition of an inch was that of “three lengths of a barleycorn.”
David I of Scotland (c. 1150) defined the old English ynche as being the breadth of a man’s thumb at the base of the nail. To be more accurate, it was customary that the thumb breadths of three men — one small, one medium, and one large — be added together and then divided by three to arrive at a fair determination of an inch.
In 1324, during the reign of England’s Edward II, the inch was redefined as “three grains of barley, dry and round, placed end to end lengthwise.”
The use of “budge” as a verb, meaning “stir, move,” was also very new; the earliest example we have is from the 1580s, and about three years before Shakespeare’s play, “The Taming Of The Shrew” which was written between 1590 and 1594, and published in 1623 .
It comes as no surprise that to refuse to “budge an inch” has become ingrained in the English language and clearly paints the picture of someone who is inflexible in changing his mind regardless of facts or laws, especially in light of the fact that in Scene 1, Shakespeare’s drunken Christopher Sly says:
HOSTESS:
You will not pay for the glasses you have burst?
SLY:
No, not a denier. Go by, Saint Jeronimy! go to thy cold bed, and warm thee.
HOSTESS:
I know my remedy; I must go fetch the thirdborough. [Exit]
SLY:
Third, or fourth, or fifth borough, I’ll answer him by law. I’ll not
budge an inch, boy; let him come and kindly. [Falls asleep]
Sly’s nonsensical response to the Hostess — “Go by, Saint Jeronimy!” — is a drunken misquoted famous line from Thomas Kyd’s The Spanish Tragedy (“Go by, Hieronymo!”) written between 1582 and 1592.
Historically Speaking 