My grandmother always told me not to walk around the house in just socks and no shoes. Is there anything to this or is it an old wives tale?
There is no law that forbids you to walk around in socks. But our sages teach us to never ignore the sayings of our grandmothers, for there is always some wisdom in them. Indeed, your grandmother's aversion to shoelessness does have some basis.
Jewish law states that one who is mourning the loss of a loved one removes their shoes. Thus walking around in socks makes you look like a mourner, and we don't even want to look like a mourner. This is part of a general Jewish attitude to death. We don't like it. We do whatever we can to stay away from it.
There are many Jewish customs that stem from the desire to avoid anything associated with death. Some people don't sleep with their feet facing the door, because that is how a corpse lies before burial. We don't speak about what will happen when someone dies, but rather what will happen "after 120 years." We wash our hands after attending a funeral, to rid ourselves of the impurity of the cemetery.
This dislike of death is not so much a superstition as an allergy. Our tradition trains us to love life and be allergic to death. Unlike some traditions that venerate death as an ideal and view life as a wretched curse, the Jewish tradition cherishes life as a blessing. Through customs that distance us from death and its trappings, the Jewish people has inculcated a worldview that is life-affirming and this-world focused.
Your grandmother had a point. Death is a part of life. But it need not be given any more space than necessary. Keep your shoes on.