dying of the light?

offofof to render Latin ab, de, or ex, in constructions where non-literary discourse would not have used it. Of greater significance was its employment from the 11th cent. as the equivalent of French de, itself of composite origin, since it not merely represented Latin de in its various prepositional uses, but had come to be the substitute in French for the Latin genitive case. Whether of might have come independently in English to be a substitute for the genitive has been much debated. In the expression of ethnic or national origin, we find of and the genitive to some extent interchangeable already in early Old English, cf. the following:
eOE tr. Bede Eccl. Hist. (Tanner) III. xiv. 210 Wæs es wer..of æm æelastan cynne Scotta [L. de nobilissimo genere Scottorum]. eOE tr. Bede Eccl. Hist. (Tanner) III. xv. 222 Se nyhsta wæs Scyttisces cynnes [L. natione Scottus]. eOE tr. Bede Eccl. Hist. (Tanner) III. xv. 222 Se wæs eac Scotta cynnes [L. de natione Scottorum].This may well have extended in time to other uses; but the influence of French de was probably a major factor in the replacement of the Old English genitive after adjectives, verbs, and even nouns by the of construction in early Middle English. The evidence, however, also suggests that an internal change in English, the loss of inflection in the definite article and strong adjective (by the end of the 13th cent. at the latest), triggered the advance in the use of the of construction as a periphrastic genitive. Beside this (a far-reaching fact in the functional history of of) the same influence is also manifest in numerous phraseological uses, and esp. in the use of of as the equivalent of French de, in the construction of many verbs and adjectives. Many of these can be clearly distinguished; but, in other cases, the uses derived from French de have so blended with those derived from Old English of, giving rise again to later uses related to both, that it would be difficult, if not impossible, to separate the two streams, with their many ramifications. The present entry seeks to exhibit the main uses of the preposition, and to show generally how far back each of these is exemplified. It has not been attempted to classify or even mention all the verbs and adjectives which are or have been construed with of; examples occur under the chief senses and uses, but the construction of any individual verb or adjective is dealt with under that word itself, where also it is shown what other prepositions share or have shared the same function with of.

To die of a malady, hunger, old age, or the like; by violence, the sword, his own hand; from a wound, inattention, etc.; through neglect; on or upon the cross, the scaffold, at the stake, in battle; for a cause, object, reason, or purpose, for the sake of one; formerly also with a disease, the sword, etc.; on his enemies (i.e. falling dead above them). In earlier use the prepositions were employed less strictly.

To assume that there is always logic to the constructions of the English language is to beg for confusion.

maybe he uses "of" cause he doesn't want to put as much emphasis on the cause of the dying thus using a shorter word. using a longer word would draw more attention to that part of the phrase.