Learn English – Bow vs Bow – etymology of the differing pronunciation

Ah, I see I should have read more closely.
I actually did some research that touches on this.

The ST- assonance (initial consonant cluster) has a long and varied and surprisingly coherent phonosemantic history, dating from a pre-Proto-Indo-European era.

I tripped over ST- while trying to figure out what style meant, in a paper on metaphors, for a literary journal named Style. As usual, there was a lot more stuff going on than I had expected.

The paper is called "Style Stands Still", and I see no reason to reproduce it here, since it's online. (The stuff about ST- starts on page 8, but it's built on the context of the first part; the paper is 20 pages long, with bibliography).

EDIT: By request, a brief excerpt from the paper:

Figure 1. st-initial PIE roots, with some reflexes in Modern English
Source: Watkins (2000), Pokorny (1959)

• *stā- ‘To stand, with derivatives meaning “place or thing that is standing”’ (Pok sta- 1004)
  style, stand, steed, stud, stay, stage, stamen, standard, stem, station, stasis, static, status, stable, stoic, store, stylite, steer
• *steigh- ‘To stride, step, rise’ (Pok steigh- 1017)
  stile, stirrup, stickle, distich, acrostic
• *steu- ‘To push, stick, knock, beat’ (Pok 2. steu- 1025)
  stub, steeple, stoop, stutter, stock, stoke, steep
• *stel- ‘To put, stand; with derivatives referring to a standing object or place’ (Pok 3. stel- 1019)
  stolon, stalk, stele, stilt, pedestal, stolid, stall, stout
• *ster- ‘Stiff’ (Pok 5. ster- 1029)
  stare, starch, stork, starve, stark, stern, strut, start, stark, startle
• *stebh- ‘Post, stem; to support, place firmly on, fasten’ (Pok steb(h)- 1011)
  stoop, staff, staple, stump, stamp, stomp, stave
• *steip- ‘To stick, compress’ (Pok steib(h)- 1015)
  stubble, stiff, stipple
• *steg- ‘Pole, stick’ (Pok 2. (s)teg- 1014)
  stake, stack, stagger
• *stegh- ‘To stick, prick; pointed’ (Pok stegh- 1014)
  stair, stick, sting, stigma, stimulate, stag

There is a strong family resemblance among the roots here. Indeed, on perusing this list, one finds a persistent cognitive image building up, with at least the following four significant perceptual properties:

Figure 2. Cognitive semantic properties of st-initial PIE roots

1. One-Dimensional: The image has only one salient major dimension
2. Vertical: That dimension is situated in an up-and-down orientation
3. Strong: The image displays rigidity, stability, and physical integrity
4. Still: The image is either unmoving, or frozen in motion

...

Not all of the characteristics in Figure 2 will be true of every Modern English word that comes from the roots in Figure 1, but some combination of the features applies to them all. For instance, although the Modern English words stamen, stile, steeple, stalk, stork, staff, stake, and stick each come from a different PIE root, all of them refer either to long rigid objects or to things characterized by such, mostly vertically oriented, and often supporting, attached, or applied to other structures by their ends. For that matter, they tend to apply to any Modern English word beginning with st-, no matter where it comes from.

My Glossary of Computing Terms: An Introduction (pub BCS, 1984) says

Field is a predetermined section of a record

which covers forms as well.

OED shows the origin is surprisingly early:

19. Computing. Any one of a number of places where a user is expected to enter a single item of a particular type of data; an item of such data; esp. one in a database record. Cf. data field n. at data n.

Originally a group of columns on a punched card.

1903 Jrnl. Polit. Econ. 11 372 The fields are to be punched in the regular order by touching the keys indicated from left to right.

Data field was apparently first mentioned in a patent:

data field n. a section of a record, esp. in a database, in which an item of data is entered; each of the particular types of data held in a database.

1929 Brit. Patent 302,314 9/9 A previous inventory perforated strip P1, the separate data fields of which give, inter alia, the following data [etc.].

It's a fairly small step to extend other earlier uses to reach the above meanings:

10. a. An enclosed or marked-out area [for playing sport]

or even

II. An area of operation or observation.
12. a. An area or sphere of action, enquiry, or interest; a (wider or narrower) range of opportunities, or of objects, for activity or consideration; a theme, a subject. Freq. with of.
b. As a mass noun: scope, opportunity; extent of material for some specified action or operation. Freq. with for.
c. A particular branch of study or area of expertise or competence; a subject. Also more fully field of study.