Apologies for the delayed reply, @cdpatton. I ran a somewhat less than fully exhaustive search through T 21218, 《一切經音義》a few days ago, but I only got time to review the file today.
I’ve uploaded the search results for any interested parties, having—albeit, somewhat hurriedly—parsed and punctuated them as well:
T 2128 一切經音義.pdf (418.5 KB)
(There were also a few misprinted characters which I’ve given in bold, red print and highlighted in yellow.)
Here is one citation which lies particularly close to your reading and, I would say, gives the most detailed definition, at least among the entries I found:
T 2128 641 a07-8:尋伺(𦙃、吏反。梵言:毗恒迦,此云尋;毗遮羅,此云伺。尋,謂:尋求;伺,謂:伺察。或思,或慧於境推求:[夕/鹿]位名尋;即此二種於境審察:細位名伺;故言尋伺。舊名覺觀者,案梵本菩提各覺,毗鉢舍那名觀,譯人不尋本語,致斯乖失也。)
Ad hoc translation:
Xun and si (Xu, li fan[qie]*. Indic word: vitakka, this is called xun; vicāra, this is called si. Xun - that is, “searching and seeking”; si - that is, watching and observing. Either intellection or wisdom [applied] with respect to seeking and inquiring into a given sphere, [being] crude, is classified as xun; precisely these same two with respect to careful observation of a given sphere, [being] meticulous, is classified as si. Therefore, it is said, “xun and si.” Regarding their having been formerly rendered jue and guan, the Indic bodhi [and] vipassanā being rendered jue and guan, translators refrained from using the original terms, resulting in this error of inaccuracy.)
*Fanqie refers to the ancient Chinese system of phonetically representing a character by employing two other characters, with the initial of the first and the final of the second representing the initial and final of the original character, respectively.
So, as I understood you to be saying, vitakka/尋/覺 and vicāra/伺/觀 denote respectively more crude or more fine strands of mental investigation into a field of dhammas. Though not explicitly stated here, I think it’s justifiable to conclude that this should simultaneously point to both a narrowing (one might also call it a “focusing”) of said “field” as well as a weakening of the volition and a calming of the activity driving the investigation. This conclusion I draw not only from what we know of jhāna practice as a whole, not only limited to this very narrow context, but also from these two Chinese words, 尋 and 伺 (and similarly with 覺 and 觀). The words synonymously associated with 尋 (including 覺, as well as 度, 逐, 繹, 理) all bespeak investigation accompanied by great movement or activity; whereas those associated with 伺 (i.e., 觀, along with 察, 候, 見, 視) simply denote watching or seeing: and, moreover, quiet watching.
To return to your analogy of observing animals, hunting animals—or, more accurately, lying quietly in wait for animals, as in an ambush—is actually the meaning given for 伺:
《說文》云:伏,伺也。伏,伺人也。
Shuowen states: “Ambush, 伺; ambush, a person who 伺s.”
Again, I don’t think the pouncing part of the ambush (伏) is so much the point here, but the spying, the quiet observation:
《方言》:自江而北謂:相竊視為伺。
Fangyan: “North of the Yangtze, watching through a chink is 伺.”
《方言》曰:伺,視也。自關而北,凡竊相視謂之伺也。
Fangyan says: “伺, watching. North of the border, all watching through a chink is referred to as 伺ing.”
All of the foregoing was taken from T 2128; so these were entries which, although taken from traditional, secular reference works, were selected by the medieval Chinese Buddhist community. But, if we do a little searching of our own, we find that the fundamental connection between 伺 ocular activity is further evidenced in the variant 覗.
And modern dictionaries give, as meanings for 伺,
- 暗中偵察。
“Inspecting in the dark.”
and, even more illustrative of the still, even passive quietude of 伺,
- 守候、等待。
“To keep and hold; to wait.”
And, of course, when we take into account 's variant pronunciation, cì, we get the word 伺候, meaning, “to wait on” (侍候), “to submit to in service” (服侍).
The quieting, the calming, the tranquilizing, as you and I both maintain, is clearly in 伺 rather than 尋, which really portrays a search (or even a pursuit) which takes place over a somewhat wider area. (Keep in mind that 尋 was also the name for a unit of measurement of length: eight traditional Chinese feet, as I recall.) I think you and I both agree not only that the Chinese terms reflect this, but that this is furthermore an accurate depiction of what a meditator should experience phenomenologically.
However, my point is, was, and shall remain that, contrary to all of the above, vitakka and vicāra inexplicably indicate the converse: that is, thinking followed by wandering. (Or, at least so it appears prima facie to someone only superficially familiar with Indic languages such as myself.)