Here Oliver Cowdery initially wrote word instead of the correct sword in the printer’s manuscript. His error was very likely influenced by the visual similarity between word and sword and may have also been influenced by the preceding words in “unto my words”. Virtually immediately Oliver caught his error here and inserted inline an s before the w (there is no change in the level of ink flow for the inserted s). This momentary error reminds us of the case in 1 Nephi 12:18 where sword was misread as word, an error that has never been corrected in any printed edition (see the discussion under that passage). Of course, here in Helaman 11:14 sword is a much more reasonable reading than word.
One potential problem here in Helaman 11:14 is that modern readers might wonder how the sword could be considered a pestilence. We expect pestilences like disease and vermin, but not the sword. Moreover, pestilence is always distinguished from the sword and from famine elsewhere in the Book of Mormon text:
And we can find similar examples in the books of Jeremiah and Ezekiel in the King James Bible, as in Jeremiah 27:8: “that nation will I punish saith the LORD with the sword and with the famine and with the pestilence”. But the King James Bible has one example where pestilence is figuratively referred to as “the sword of the Lord”, although the literal sword of David’s enemies is not called a pestilence:
David chose the third of these curses, and indeed the angel that kills seventy thousand men is seen by David as “having a drawn sword in his hand” (1 Chronicles 21:14–16). Thus the sword of the Lord can be referred to as a “pestilence in the land”.
The Oxford English Dictionary, under the noun pestilence, gives examples from Middle and Early Modern English with figurative meanings for the noun that will work here in Helaman 11:14. For instance, definition 3, designated as obsolete, states that a pestilence can be ‘that which plagues, injures, or troubles in any way’. In fact, one of the citations from Early Modern English specifically refers to war as a pestilence:
Thus the reference to the sword, the symbol of war, as a pestilence is quite acceptable in Helaman 11:14. Despite the uniqueness of the phrase “the pestilence of the sword” in the Book of Mormon text, the critical text will maintain this reading.
Summary: Accept Oliver Cowdery’s corrected reading in Helaman 11:14, the use of sword in “the pestilence of the sword”; the reference to the sword (that is, war) as a pestilence is supported by usage from Early Modern English, including the King James Bible in 1 Chronicles 21:12.