Need the quest:
http://bdocodex.com/jp/item/31052/?sl=1
Need a lot prequests.

Need this quest chain first: Palm forest boy

After doing every single quest and wasting loads of energy I got the knowledge, you need:
Helping hand quest from node manager and its whole chain, requires 10 energy to check palm trees but pretty quick.
and the whole palm forest boy chain : requires about 50 energy to do chain+ a bunch more for amity game and a wood axe to cut some pams.

There is a list of things you need to do in order to get this knowledge. You will need quite a bit of energy to complete it as well.

1. Start the Palm Forest Boy quest chain by speaking to Yasum
2. Once you get to the point in the quest chain where you need to find the boy's book, it is on the 2nd floor of the Tavern located near the docks in a bookshelf. It requires some energy to retrieve.
3. You will eventually need to get Dudora Doriven to 250 amity to keep the quest chain going. The best chain for this is: Graule -> Buta -> Ami -> Buroma -> Yasum -> Sankamu
4. When you get to the point where to need to deliver 15 palm timber to Larina, you will need to chop palm trees. The game will highlight trees that are far away, but there are plenty near the town to cut down. Ami is a material vendor in the town that will sell you an axe for 50,000 silver.
5. After some running around, you will need to find Areha's three journals. They are in the box directly to the right of the hut that is next to Rohu. After that, you will need to get Areha's journal off the cabinet and then open the box to the right of that.
6. After the Palm Forest Boy quest chain, you need to speak to Rohu again to start the Helping Hand quest and proceed through the "Votudig is Okay" quest chain.
7. Once the quest chain is done, you will gain the Votudig knowledge.