It just occurred to me that I've never seen the term on the forum before.
It was pretty common in my area. There was a group, a clique really, of regular pioneers, mostly stay-at-home mom types who placed the "try-oneer" label on newly-appointed regular pioneers. It was their way of cementing their importance. Mostly they didn't want some young newly-appointed MS messing things up for them. They had a routine down. They liked to do service a certain way. They were used to meeting at a certain hour, taking coffee breaks at a certain hour, getting car groups together composed of certain people and working certain territories, and they didn't want their routine interrupted.
So when a new batch of pioneers got appointed in September, they'd slap the try-oneer label on them as a way of diminishing them and defending their turf. "We've been pioneering for 10, 15, 20 years, and you're still wet behind the ears. You're lower on the pecking order than we are. Don't even think that you're our equal. If you try to shake things up, we will make your life a living hell." That kind of thing. I guess it was their way of saying that the new pioneer hadn't proven himself yet. He was "trying out" pioneering to see if it was for him. This new pioneer wasn't like them. He hadn't shown years of commitment to pioneering.
If the new pioneers kowtowed to the clique, they'd eventually be accepted as "one of them" and the try-oneer label would be dropped. If not, they'd try their damndest to make the new pioneer's life as miserable as possible. I was always put off by the blatantly unchristian behavior.
Was this term common in your area or is it a local thing?