We'll be singing some old words in our time of musical worship on Sunday. I thought it'd be interesting to think a little bit about what they mean and why we use them.
Definition of 'thou:' second person singular pronoun, archaic (replaced by 'you'), sounds formal when used today
Did you know that, centuries ago, people used 'thou' as familiar and 'you' as formal? It's kinda like tu/usted in Spanish for the hispanohablantes out there. You would say 'thou' to close friends and family, reserving 'you' for formal situations.
When Tyndale translated the Bible into English, he used 'thou' to refer to God intentionally to show the intimacy in the relationship. When King James authorized the King James Version a century or so later, it lifted over 80% of Tyndale's language word for word, including his use of the word 'thou.'
Over time, French influence on the English language and the growing popularity of formal addresses pushed 'thou' out of usage in common speech. It's usage was preserved, however, in religious settings, due to it's inclusion in the King James Version of the Bible.
Because these religious settings were more formal than people's everyday context, 'thou' began to take on a more formal feel and usage. And that's what's been passed down to us.
We use it today mainly because of it's sound. It can help rhyme schemes and has a smoother sound than 'you,' so it's commonly found in hymns and music (which is where you'll hear it tomorrow).
God doesn't require us to use 'Thou' when we address him, but some Christians still use it in prayer. Some Christians use it in order to be more reverent and respectful. Some also use 'thou' because it fits their tradition and the way they were raised. Some use it because they want to sound more smart and holy than they actually are. Thou canst usually tell the difference (Thou wilt not fool us with thy fancy-sounding prayers, Fancy-sounding Pray-er. We're onto thee).