I would guess that they originally put the siding on the house due to rotten logs. They probably did not know where to go to get he problem fixed or could not afford it.You will have to have it sand or corn cob blasted to remove any old finish that may exists, most likely have to have it sanded if the old finish is thick,I would recommend a borate treatment be applied and if there was problems with the chink before it will have to be addressed. Then of course, a stain and clear coat must be applied. It's going to be hard to tell what you have going with rotten logs until the siding is removed. If there are exposed logs on the interior you may be able to take a hammer and bang on them. Listen for a dead or dull thump to find the rotten logs. Good luck.