In both Titus 2:14 and I Peter 2:9, the word "special" replaces "peculiar," as used in the King James Version. Peculiar was not used in the sense of "odd" or "weird," but as being "distinctive" in a singular, good way. It is likely due to a desire to avoid the suggestion of "odd" that modern translators have changed it to "special," which carries a more positive implication.
A person may be distinctive because he is nine feet tall and sports purple hair—and therefore odd. On the other hand, a person might be exceptionally handsome or have an engaging accent. Perhaps an individual's distinctiveness lies in an artistic, athletic, or mathematical ability. Maybe he or she has a photographic memory or has overcome a debilitating affliction.
However, none of these distinctions matter in terms of why Christians are peculiar. In Titus 2:14, Paul uses the adjective form of the Greek word translated "special," while in I Peter 2:9, Peter uses the noun form of the same word. Paul also uses the noun form in Ephesians 1:14, writing, ". . . who is the guarantee of our inheritance until the redemption of the purchased possession, to the praise of His glory." Here, it is translated as "purchased possession," which actually comes closest to its literal meaning: "an acquisition, an obtaining, a possession."
In Titus 2:14, the Greek term literally means "one's own" or "one's own possession," which is why His people are special. They are God's own, and so are therefore distinctive because nobody else owns the called-out ones. In I Peter 2:9, some modern translators have replaced the King James word "peculiar" with an expanded version, something similar to "His own special possession," implying the same specialness and distinctiveness due to ownership.
Special means "surpassing what is common or usual; exceptional; distinct among others of a kind." We have been made unique, separate from others, peculiar, distinctive, and special from God's point of view because He has obtained, acquired, or purchased us with the blood of Jesus Christ. It is who purchased us, our purchase price, and His reason for purchasing us that motivated the translators to use the word "special." It conveys the sense of uniqueness.
The New Testament Commentary remarks that "His own possession" or "a people, His very own" appears so often in Scripture in somewhat different forms that it ought to be considered as part of its technical phraseology. It is a point God clearly wants to impress on us through sheer repetition.
Why has God gone to this trouble and expense, an expense that cost Him the most precious of all prices? The last phrase in Ephesians 1:14 succinctly states why: "to [for the purpose of] the praise of His glory." I Peter 2:9 and Titus 2:14 say essentially the same thing. However, Philippians 1:9-11 states more specifically and expansively how His special people offer praise:
And this I pray, that your love may abound still more and more in knowledge and all discernment, that you may approve the things that are excellent, that you may be sincere and without offense till the day of Christ, being filled with the fruits of righteousness which are by Jesus Christ, to the glory and praise of God.
We, the called-out ones, are unique because of who owns us, because of the price He paid to redeem us from our former owner, and in that we, the purchased possession, are to glorify Him.
John W. Ritenbaugh
Our Uniqueness and Time