There's apparently only so much room in the Christian jargon lexicon. Church folk seem to love a bit of insular language – weird phrases that only make sense to those within the fold – but as Christian culture changes and new examples of the phenomenon appear, there are others which find themselves cast into the cold. With the advent of 'life-on-life discipleship', 'intentional leadership' and 'missional communities' there are inevitably a few words and phrases that have begun to drop out of common usage.

Perhaps the most profound example of this is the word 'backsliding', or its more accusatory brother, 'backslider'. When I became a Christian two-and a-half-decades ago, you couldn't move in a church for hearing the word. It described, rather visually, the idea that someone was slipping backwards in their faith journey; that sin had crept in and sent their transformation into the likeness of Christ into sharp reverse. Just as 'insecure' is just about the most stigmatising label you can apply to a teenager, 'backslider' felt like the worst kind of judgment from your peers. Used to – literally – cover a multitude of sins, it became an easy way to delineate the righteous from the unrighteous within the Christian community.

That description makes the word, and the motivations for using it, sound petty and horrible. Perhaps that's why we've allowed it to drop out of common usage; there's no place for judgmentalism in the church, and the puritanical thinking that underpins it is something we're thankfully starting to leave behind.

Yet I wonder whether as we dispense with this phrase, we might also be losing a very biblical concept: that of lovingly watching out for each other's Christian journey. That's not code for 'waiting for each other to slip up', but is about a genuine concern that our fellow-travellers on the road of faith don't inadvertently find themselves falling into a ditch. In Galatians 6:1, Paul writes, 'If someone is caught in sin, you who live by the Spirit should restore that person gently.' He doesn't tell us to pronounce judgment on or label each other, but he does suggest we should care enough about one another to confront sinful behaviour.

So while the word 'backslider' is unhelpfully labelling and judgmental, I wonder whether its disappearance from the Christian phrasebook is about more than that. It seems to me that in the last few years, as we've perhaps begun to get a firmer handle on God's grace, we've become much less concerned in church culture about the seriousness of personal 'sin'. The reality of hell and judgment have been publicly questioned but the debate has been left unresolved; the metaphor of a faith journey has – I think helpfully – replaced the simplistic idea of a single-moment conversion. Perhaps as a result of some of these shifts in popular theology, our approach to a range of behaviours that might once have been considered evidence of 'backsliding' is now much more permissive.

Which prompts the question: have we stopped talking about 'backsliding' because it's a horrible, graceless word, or because so many of us have become guilty of it? The trouble with drifting away with God is that the act itself tends to urge us towards self-justification and denial, so it's natural we might feel so uneasy about a word which puts a finger on the things we enjoy but perhaps shouldn't.

The Christian singer Martyn Joseph wrote possibly the only song on the topic. It included the repeating chorus, 'I'm a liberal backslider/been sliding about 10 years/people ask me how I'm doing and I confirm all their fears/ I'm swearing like a trooper and I'm drinking like a bum/ I'm a liberal backslider but it sure is a lot of fun.'

Joseph was deliberately overstating the point to send up conservative Christian culture, but he also illustrates not only the problem with the word but with the culture that rejects it. Judgmentally labelling other people isn't a fruit of the Spirit, but then neither are swearing or heavy drinking.

We're probably better off without any Christian jargon at all, and 'backsliding' is a particularly ridiculous example of when our culture can become alienating, insular and a little unpleasant. Yet as we stop using the word, perhaps we shouldn't completely lose touch with the concept. Sin is serious – if we believe the Bible we simply can't get past that – and faith journeys can move in two directions.

The Bible tells us to watch out for each other, not to wait hopefully for our fellow Christians to trip up so that we can label them.

Martin Saunders is a contributing editor for Christian Today and the deputy CEO of Youthscape. Follow him on Twitter @martinsaunders.